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Before electrical recording was developed in 1925, recordings were made mechanically without using electrical signals, a process known as “rappa fukikomi” (horn recording) in Japan.

With this acoustic recording method, performers would take turns to go and play in front of the horn that collected the sound.

In 1924, "Western Electric" developed a method of electrical recording, which "Victor Talking Machine Company" and "American Columbia" adopted in 1925, calling them “Orthophonic” and “Viva-tonal” respectively.

In 1933, Victor Talking Machine Company changed the name “Orthophonic” to the familiar “High-fidelity Recording.”

Victor Company of Japan began using this name in 1936.

1925 was the year that Japan first began radio broadcasts, and it was also the year that silent films really gave way to “talkies,” thanks to Western Electric’s development of the Movietone sound system.

Western Electric also developed a speaker system for movie theaters that combined their legendary 555-W wideband field-coil compression driver with a large 1.5m 15 A horn. This marvelous historic cinema sound system was even widely used throughout Japan in cinemas and public halls, etc., after the end of WWII.

The transition from acoustic recording (mechanical recording) to electrical recording came with an astounding improvement in the range of reproducible frequencies; although acoustic recording could capture from 300 Hz to 3 kHz (three octaves), electrical recording could capture from 100 Hz to 5 kHz (over five octaves).

In 1944, during the war, "full frequency range recording" (ffrr) was announced. Developed by British Decca mainly for military use, it could capture from 30 Hz to 12 kHz.
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Besides the attempts beginning in 1925 at high-fidelity sound reproduction, there was a desire to make audio recordings for movies and play them back in sync with the silent films.

Although they wanted to record approximately ten minutes of audio on one record for one silent film, 12" (30 cm) 78-rpm SP records could not satisfy this requirement. Three options were reducing their rotational speed, taking time to increase their recording density, or increasing their diameter, but increasing their recording density would require reconsidering materials and manufacturing techniques, so the quickest and easiest option was chosen:

16" record with a rotational speed slow enough to record 10 minutes of audio. This meant selecting a rotational speed of from 33 to 40 rpm. To match the playback speed of the records with the movie projector, synchronous motors (which are synchronized with the frequency of the power supply) with simple gear ratios were needed.

A rotational rate of 33 1/3 rpm can be obtained by using an 1.800-rpm synchronous motor running on American 60 Hz mains with a reduction ratio of 1:54, or by using a reduction ratio of 1:45 with a 50 Hz, 1.500-rpm synchronous motor.

The 45-rpm disks released in 1949 could be played back with a 60 Hz, 1.800-rpm synchronous motor with a reduction ratio of 1:40; but not with a 50 Hz, 1.500-rpm synchronous motor with a reduction ratio of 1:45, as there was a small difference in speed.
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Incidentally, US firm Columbia Records worked on realizing microgroove recording (higher density with narrower grooves and closer groove spacing) to compete with RCA Victor.

• Anmerkung : Sorry, es war genau umgekehrt. Columbia stellte 1947/48 die neue 30cm Vinyl-LP vor und RCA kam 1949 etwa ein Jahr später mit der 45er Vinyl-Single hinterher.

The combination of reducing rotational speed and using microgrooves eventually led to the LP, but improved materials, etc., were needed to reduce noise, delaying the LP’s commercialization until after WWII.

Three-dimensional sound also has a long history.

In 1845, the German physiologist Ernst Heinrich Weber demonstrated the “binaural effect,” where people could determine the distance and direction of sound sources by using both ears.

In 1928, a Mister W. Bartlett Jones of Chicago filed a patent for a “Method and Apparatus for Audition” that described a binaural recording system involving a dummy head.

Dummy heads are still used today to solve sound lateralization problems with headphones. The basic patent for three dimensional sound reproduction from disk records is British Patent No. 394,325 “Improvements in and relating to Sound-transmission, Sound-recording and Sound-reproducing Systems,” filed by EMI’s Alan Blumlein in 1931, but it was not realized until 1957 that this 45/45 system was applied commercially by Westrex Corporation, a division of Litton Industries which acquired it from Western Electric.

Although Decca soon followed with stereo records cut with a vertical-lateral technique, ultimately it was the 45/45 system that became the most widely used.

On April 27, 1933, Bell Laboratories, who had been researching high-fidelity sound reproduction and three-dimensional sound since the beginning of 1920, conducted a three-dimensional sound reproduction experiment over telephone connections between Washington and Philadelphia.

The Philadelphia Orchestra was conducted by Alexander Smallens while Dr. Leopold Stokowski in Washington manipulated the controls. This experiment was overseen by Dr. Harvey Fletcher, Bell Laboratories’ Director of Acoustical Research, who later laid out the conditions for high-fidelity reproduction (Table 5.1).

Table 5.1 Conditions for high-fidelity reproduction by Bell Lab’s Dr. Fletcher from the 1933 experiment.
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• (1) Transmitted noise is quieter than the noise pollution in the room where the audio is reproduced;
• (2) Peak dynamic range of 100 dB SPL is required to reproduce symphonies;
• (3) Distortion caused by nonlinear transmission characteristics is too small to distinguish;
• (4) Frequency range must exceed the range of human hearing;
• (5) Positioning is well defined.

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True stereo (orthostereophonic) was the result of these experiments 80 years ago. If Dr. Fletcher might appear before us, then we should worry that he might urge us forward by telling us what little progress we have since made. Individual recording technologies will be discussed in more detail below.

Microphones are transducers (Wandler) that convert sound into electricity. First applied to practical use in telephones, they were later developed for broadcasting. One of the earliest was a carbon button microphone in the mouthpiece of the 323 W telephone, introduced by Western Electric in 1920.

One of these was used in Japan’s March 1, 1925 experimental radio broadcast. A regular broadcast on March 22 used a Western Electric Model 373 double button microphone.

As these microphones did not have a sealed construction, they had a defect where noise increased as moisture (Feuchtigkeit) entered through gaps and deteriorated the mobility of the carbon granules.

Various measures were taken to ensure the mobility of the granules to solve this. Initially, the carbon granules would solidify during use, and they would be periodically taken out and mixed to loosen them. To solve this, the balanced armature, which is popular in modern earphones, was introduced. This method increased the mobility of the carbon granules by setting up a barrier inside the microphone, and also improved microphone bass characteristics.

Later, in the 1930s, Japan began importing high-power transmitters from Marconi's Wireless Telegraph Company in Britain and then Telefunken in Germany to increase the power of Japanese radio broadcasting stations.

Included with these transmitters were Reisz microphones, which had a sealed construction using carbon granules and marble. Some Reisz microphones were later developed in Japan; notably the MH microphone, which was developed by and named after Noboru Marumo and Kichibe Hoshi at NHK Science and Technology Research Laboratories in 1932.

The MH microphone (Fig. 5.1) used a hollowed marble block filled with carbon granules, and had a mica diaphragm and a carbon electrode attached to the front, with a filling port for the carbon granules on the side.

Information regarding this is, probably because know-how regarding the carbon granules was kept secret at the time.

When this microphone was left for extended periods (around 10 hours), the carbon granules would gradually settle, and excessive current would flow because of the decreased internal resistance, causing sensitivity to drop.

For this reason, before use it would be held upside down and gently tapped to loosen the carbon granules, and only used after the current had returned to the correct level.

Reisz microphones used marble, but microphones using Setoyaki ceramic instead of marble appeared after WWII, which were used with great success in megaphones used in the general elections for the Upper and Lower House under the new constitution.

Their development was handled by Shiro Kato (former auditor for Aiphone Co. Ltd.), and they were commercialized under the guidance of Yoshiro Tomita (who formerly worked at NHK STRL and JVC).

Ribbon microphones and other velocity microphones appeared in 1933, with microphones such as the Altec 639B, the RCA 44-BX and the RCA 77-DX being the main units used in recording studios right through until after the war.

The Altec 639B, called the “iron mask” for its appearance, is shown in Fig. 5.2. This microphone was not a simple ribbon microphone but a hybrid that including both moving-coil and ribbon elements.

When ribbon microphones came into frequent use in Japan, the demand for their loose ribbons (die ausgeleierten Bänder) to be repaired in Japan soon appeared. This state of affairs prompted Tokyo Denki (Tokyo Electric Company, now Toshiba) to produce the “Type A,” which in 1937 was the first Japanese ribbon velocity microphone.

This microphone, which was also used to record the "imperial edict" at the end of the war and can be seen to the right of the disk recorder in Fig. 4.6, is very similar in appearance to the RCA 44-BX shown in Fig. 5.3. During the period of reconstruction after the war, Tokyo Denki developed a series of ribbon velocity microphones such as the Type B, the Type E, the Type F, etc., mostly with Masao Shimabara (formerly of Tokyo Shibaura Electric Co., Ltd.).

As these velocity microphones happened to have a tone suited to enka (Japanese ballads) singers and traditional Japanese musical instruments, they were widely used to record many of Japan’s post-war hit songs. Another velocity microphone, the famous RCA 77-DX, was used to record hit songs by Hibari Misora and others who graced the period immediately after the war, and it is sometimes used in recording even to this day.

The RCA 77-DX is shown from the front in Fig. 5.4, and from the back in Fig. 5.5. As can be seen in Fig. 5.5, the microphone had a directional pattern selector switch on the back. A label stating that it is “exclusively for traditional Japanese music” is attached, indicating that it was used to record many famous Japanese recordings.

With regard to moving-coil microphones and headphones, the foundations of which were laid by Bell Laboratories, the Western Electric No. 618A was released in the early 1940s, and then introduced to Japan by their business partner NEC.

Despite their good characteristics, prior to the war it was known that condenser microphones had problems with unstable operation caused by electrical discharges, etc., and it was not until after the war that these problems were solved. It was then that condenser microphones such as the Telefunken M49 (Fig. 5.6) appeared.

With regard to Japanese condenser microphones for broadcasting stations, in 1953 the CU-1 unidirectional microphone (Fig. 5.7) was developed after being devised by NHK STRL.

The development of this microphone was said to have been fraught with difficulties, including the fact that studios at that time were brightly lit by incandescent lights and the radiant heat caused the diaphragms of microphones to lose their tension, while a lack of insulation caused noise.

In 1955, Tokyo Tsushin Kogyo (now Sony) produced the C-37A microphone, which was modelled after the CU-1. The C-37A had four small openings at the back of the single diaphragm of the capsule, enabling omnidirectional or unidirectional modes to be selected by opening and closing a shutter (internal screw).

The sound of this microphone was criticized by some for its lack of brilliance in picking up remote voices, but it had an established reputation for picking up stringed instruments such as the koto and the shamisen, so it made a place for itself in Japanese broadcasting stations.

The C-37A later came to be widely used not only in Japan but also overseas in the studios of private broadcasting stations and recording companies.

Many new microphones appeared during the 1960s and 70s, such as multidirectional microphones, which can clearly pick up multiple sound sources; close-talking microphones, which are indispensable for television broadcasting; mid-side (MS) stereo microphones, which can pick up stereo sound with a single microphone; dummy head microphones, which do not produce the lateralization that can be heard with headphones that normal recording produces; and other kinds of microphones for various purposes.

The Neumann SM 69 stereo condenser microphone (Fig. 5.8), which could pick up stereo audio on its own, was widely used in concert halls, etc. Neumann also developed the KU100 dummy head microphone (Fig. 5.9).

Dr. Karl Schoeps, who developed many products at Schoeps GmbH, designed microphones with excellent acoustic qualities, and introduced innovations such as microphones with low optical reflectivity that would not appear conspicuous in television programs (Fig. 5.10).

• Anmerkung : Die deutsche Firma hieß zwar Dr. Schoeps Schalltechnik Karlsruhe, aber der Technische Direktor war Dipl.-Ing. Jörg Wuttke, der diese Entwicklungen initiiert und geleitet hatte.

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In 1924, Mototaro Eguchi (formerly of the Technical Research Institute of the Japanese Navy) discovered the electret, which is a phenomenon where an electric charge remains after polymer materials are cooled and solidified under a strong electric field.

The researchers at the Technical Research Institute of the Japanese Navy are now thought of as pioneers in the realm of electronics, having conducted groundbreaking research in fields such as materials for crystal microphones. Some are now connected with Rion Co., Ltd.

Although the patents concerning Eguchi’s electret phenomena covered nearly all applications regarding electroacoustic transducers, nearly 40 years passed since its discovery before the electric microphone was invented at Western Electric in 1962.

In 1968, Sony developed an electric microphone as small as the end of a person’s little finger. They then built it into their TC-1160 cassette player, which they released on December 1. of 1968, the same year, blazing a trail for multi-purpose microphones in devices other than telephones.

Microphones must pick up sound from very low pressures to high pressures across the entire range of audible frequencies without distortion and with a sufficiently low residual noise level.

This means working to improve their sound qualities and characteristics, but in spite of the efforts of many pioneers, an ideal microphone still does not exist that can evenly pick up sound waves from any direction and from any position in the sound field.

Even omnidirectional microphones (which are considered nearly ideal) may have a far-from-ideal characteristic at the back and the sides, though they may have a relatively flat frontal characteristic. Directional microphones (which have more problems) have a relatively flat characteristic in one direction but usually have a poor base response.

It is desirable for directional microphone to have a warm, flat frequency response even with lower levels, but in reality they usually sound thin from any angle other than the diaphragm axis.

Making omnidirectional microphones pick up sound properly from all angles is also difficult. Although microphones that can evenly collect both direct sound (arriving directly from musical instruments) and reflected sound (arriving after undergoing reflection) are desirable, and although many microphones can evenly collect direct sound, most microphones can only collect reflected sound and other indirect sound as garbled noise.

In 1970, Nippon Columbia joined forces with the Danish company Brüel & Kjær Sound and Vibration Measurement A/S (B&K) to re-evaluate microphones with great recording characteristics. Takeaki Anazawa (former director of Nippon Columbia Co., Ltd.; now director of the Japan Audio Society) participated as a representative of Nippon Columbia.

The famous Danish recording engineer Peter Willemoës acted as an intermediary for the two companies.

At the time, microphones for measurement and microphones for recording belonged to completely different worlds. There was hardly any communication between engineers, both parties used different connectors and cables, and they even had completely different ways of powering their microphones.

Measurement microphones needed to always have a flat frequency characteristic over a wide range of temperatures, but recording microphones needed to be easy to use, have a distinctive sound quality, and have low noise.

The purpose of Anazawa "et al.’s" review was to cultivate the strengths of both types of microphone, and they attempted to take advantage of the flat characteristic of measurement microphones, the low noise of recording microphones, easy-to-use connectors and cables, and power supplies.

As the 1970s drew to a close, B&K trial manufactured field-type recording microphones that could evenly capture direct sound, and pressure microphones for recording that could evenly record indirect sound in the recording field, and Nippon Columbia’s European experiments in digital recording began. The characteristics of these trial microphones are shown in Fig. 5.11.

Although both types of microphone are omnidirectional, they both have different characteristics. The field-type microphone only has a flat frequency characteristic on the diaphragm axis, with reduced treble at other angles.

On the other hand, with the pressure microphone, treble is increased on the diaphragm axis, with a flat frequency characteristic being obtained at an 80-degree angle, and although the characteristic changes at angles off the diaphragm axis, a flat characteristic is obtained as a whole.

A flat characteristic can be obtained for both direct and indirect sound with a pressure microphone if the diaphragm axis is angled at 80 degrees to the music.

This joint investigation and trial manufacture with the Danish company B&K was carried out with the coming era of digital recording media such as the CD in mind, and many recordings were introduced that were captured by these trial microphones in 1982 when the CD was introduced.

A large number of these microphones were used in February 1985 in relay broadcasting the performance at the reopening of the Semperoper in Dresden (on the 40th anniversary of its bombing) to not only West Germany, but also the whole world.

Opera is a rather plain genre, but this did not stop the relay broadcast from gaining an extraordinary rating of 19% in West Germany.

The successors of these microphones are still being manufactured today, over 30 years since the adoption of the first prototypes, and they are still indispensable where sound quality is important.

Direct sound from musical instruments on a stage is not difficult to capture with a flat frequency characteristic.

By comparison, indirect sound reflected by the surrounding walls is difficult to capture with a flat frequency characteristic, and in many cases it sounds distant and lacks focus.

Direct sound microphones had always been placed closer to instruments to avoid this problem, but this creates a vicious circle where indirect sound sounds even further away (relatively) as a result. This vicious circle was solved by the introduction of pressure microphones, which can capture indirect sound with a flat frequency characteristic.

Sound capture is called pickup, and in historical mechanical sound capture (acoustic recording), singers and musicians would stand in front of the horn and play in quick succession.

Later, with the introduction of electrical recording, multiple microphones came to be used.

Three-channel stereo, which placed the solo singer (who required adjustment) in the center and the accompanying band in the left and right speakers, became common in the American pop music recording scene in the 1950s, where it was sarcastically called “three-channel monaural.”

Three-track recorders were introduced for this (by Ampex), and the number of tracks increased continuously until it reached 16 in the latter half of the 1960s.

Later, 24- and 32-track recorders appeared, and some recordings even used multiple 24-or 32- track recorders. The number of microphones used increased with the number of tracks.

When reproducing sound in stereo, the locations of the left and right speakers are the actual sound sources where the actual speakers are, making localization especially precise.

The center, where the sound image is located between the left and right speakers, is not as precisely localized as it would be with a real sound source, but it is located especially precisely among virtual sound sources.

As this precise positioning is desirable for solo singers in pop music and announcers in radio and TV programs, the tendency to emphasize the center was widespread from the early days of stereo, and three-channel stereo appeared for the same reason.

On the other hand, with classical music and traditional Japanese music, etc., even when several microphones are used to pick up sound in concert halls and other spaces full of relative reverberation, there is a great deal of sound leakage between the microphones, making results similar to those obtainable with multiple microphones in pop music recording difficult to achieve.

Moreover, volume balance often had to be maintained between all the instruments in the hall by repeated practice. Care was needed in such cases to reproduce the atmosphere of the hall. Recording engineers disliked making any particular location more distinct than any other, desiring positioning unlike the three-channel mono used for pop music, and captured sound with the aim of recording stereo, but not three-channel stereo.

The methods of using the actual microphones in the pickup methods described above can be broadly classified into

multi-microphone pickup (which uses a large number of microphones) and
one-point pickup (which uses a small number of microphones).

Overall, multi-microphone pickup is good when recording in a sound space such as a studio that lacks sound volume balance, and usually microphones are placed in close proximity to each instrument to make later adjustment possible.

Then the output of each microphone is collected at a mixing console, and the sound is balanced in post-production. On the other hand, one-point pickup is carried out on the premise that the sound among the instruments is already balanced, so the microphones are not placed nearer to the musical instruments than is necessary.

In cases where the sound is balanced in the studio or hall where the performances are held, it suffices to place a microphone that can capture direct and indirect sound in the best location.

Generally, if multiple microphones are placed near a sound source and their output mixed electrically, a comb filter is created, making the sound remarkably muddy.

To avoid this muddiness, it is important to take care to ensure that the same sound does not spill over to other microphones. Multi-microphone pickup therefore uses microphones placed near the musical instruments to prevent spill.

As microphones are placed in close proximity to instruments in such cases, they need to be able to handle large (sound-) inputs without distorting.

The transition from mono reproduction to stereo reproduction brought many changes and captivated many people. The ortho-stereophonic system appeared, which, aiming to achieve true stereo, opened up possibilities for reproducing the spread of sound sources using sound field data on the playback side.

In the early days of stereo, various attempts were made to convey the atmosphere of the original sound field (including the sound fields of concert halls or music clubs, or sound fields synthesized in studios during production). Later referred to as sound field reproduction, these attempts can be broadly classified in the three categories shown below.

This is a method where recording is carried out in the same way as for normal 2-channel stereo, and the recording is processed at the time of playback to recreate a sound field.

In one form of early stereo called ensemble stereo, there was a spread control knob called a DSC that adjusted the spread of the sound image to the left and the right.

Anmerkung : Das gibt es heute noch in den Rundunkanstalten in Deutschland, der Stereo- oder Correlations-Anzeiger, ob die Balance stimmt - insbesondere beim gemixten Mono-Signal.

This calculated the sum and the difference of the left and right signals, adjusted the levels of the sum and the difference, and returned the signals to the left and right channels.

Emphasizing the sum causes the left-right spread to narrow, and emphasizing the difference causes the spread to increase.

Listeners rotated this knob to adjust the spread to an optimal setting for the acoustic properties of the room, the positioning of the ensemble stereo, and the listener’s personal preference, before sitting back and listening to the reproduced sound.

Generally, the spread of the sound image varies due to the correlation between the sound arriving at the listener’s left and right ears, and it is possible to quantitatively measure it by the cross-correlation function between the ears. This method of evaluation is also used to evaluate architectural acoustics.

In 1961, a stereo with a spring reverberation (künstlicher Hall mit Federspiralen) unit was released. By using this stereo, reverberation (reverb) could be added at home. The second half of 1970s saw the introduction of digital signal processors (DSPs) in sound reproduction systems with reverb functions, making it possible to add electronic reverb (which was called “sound field generation” at the time).

This kind of reverb function was limited by the fact that the reverb that was added that was different from the optimal reverb selected and introduced for the program source that was used as the subject of pickup
and recording.

It also had the drawback of being unable to decrease the original reverb, only increase it.

In 2010, revolutionary sound field reproduction technologies that broke down the above limitations appeared, and the continued development of the old yet new topic of sound field reproduction is anticipated.

This reverb control technology was invented by Kinoshita and Nakatani "et al." of NTT Communication Science Laboratories.

This invention is based on the fact that reverberations are repetitions of sound that have already arrived, and it analyses the audio input and decomposes the sound into direct sound and reverberant sound.

If they can be separated, then the proportion of each can be adjusted and used to construct a signal for playback. This method makes it possible to reduce the amount of direct sound or reverberant sound added to the sound in the original program source, and it also makes reducing the amount of reverb contained in the original possible.

Methods such as dummy head (Kunstkop-Stereophonie) recording fall into this category and although 2-channel stereo is used, pickup is carried out with the aim of reproducing the sound in a specific reproduction environment, so these methods are for sound field reproduction in specific reproduction environments.

Although dummy head recording has been used for a long time as a method of achieving sound field reproduction, its spread was hindered by its lack of compatibility with speaker reproduction and the difficulty of adapting existing production techniques for music program sources that were developed with speaker reproduction in mind. These problems have persisted since the beginning, and they remain as yet unsolved, even today.

On the other hand, the spread of portable audio has caused the number of people (especially young people) who enjoy audio through headphones or earphones to increase.

Ironically, because music recorded on dummy heads is nearly nonexistent on the market, these headphone and earphone users are still listening to recordings made for speaker reproduction, and they are enjoying music without being able to localize sound images in front of them (called lateralization).

This category covers methods for reproducing sound fields using two or more channels, such as 4-channel and 5.1-channel transmission systems.

In the latter half of the 1960s, the entire audio world was fascinated with (analog) 4-channel audio, but the key users were indifferent.

It was amidst this state of affairs that in 1969 Tanetoshi Miura of Hitachi Central Research Laboratory (formerly president of the "Acoustical Society of Japan") conducted psychological evaluation experiments into 4-channel audio in cooperation with "Nippon Columbia" (which was 1969 just about to go under the umbrella of the Hitachi Group) using a diverse assortment of bands.

Although some variation was found to be caused by speaker placement, pickup methods, and music genre, the results were extremely disappointing: regardless of how much effort was spent to make 2-channel stereo into 4-channel, the effect was less then half of that obtained by making mono into 2-channel stereo, and substituting 4-channel for 6-channel or 8-channel resulted in only quarter of the improvement obtained by going from mono to stereo.

The results showed that even with four channels, it was better to place the speakers to the sides rather than to the back.

There are two types of sound field reproduction: passive sound field reproduction that can recreate the atmosphere of a hall as described in 1) above, and surround sound, a more active method of sound field reproduction which places the sound image on all sides.

In early the early 1970s, 4-channel records that could make surround sound practical became a popular topic, beginning with a matrix format 4-channel record announced by Sansui Electric Co., Ltd. in June 1970.

This matrix format 4-channel record used a normal band music signal created by a matrix encoder before cutting, which was then used to cut the disk.

Because the signals were passed through a matrix decoder during playback, despite the fact that the cutting itself had a large vertical component in the groove, the grooves were not very different from those found on ordinary records.

In September 1970, JVC unveiled a discrete 4-channel record called the CD-4, which is described in more detail in section 5.4.

Then on June 25 of the following year, JVC released “Wonderful CD-4 Sound” (CD4B-5001), the world’s first discrete 4-channel record (Fig. 5.12).

Although many interesting technical endeavors were attempted with the CD-4, it unfortunately failed to gain popularity.

The biggest reason for this failure is thought to have been the quality of the content itself. Few great pieces of music have been composed for surround sound that can localize in all directions.

One was “Requiem,” composed by the French composer Hector Berlioz, which premiered at the "Hôtel des Invalides" in Paris, but no other great pieces followed, and there were very few pop masterpieces.
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In cinema on the other hand, there are works which take the location and movement of the sound image into consideration during production and playing these using 5.1 channel or 7.1 channel surround sound is effective in movie theaters or in the home.