DTS 5.1 Music Disc (1997 – early 2000s)

The DTS 5.1 Music Disc was a Compact Disc format offering surround sound audio, usually in the 5.1 configuration. The discs would play in a standard Compact Disc player, but without the use of a DTS decoder all that would be heard is white noise. The potential confusion between DTS 5.1 Music Discs and standard Compact Discs meant some retailers were reluctant to stock them. There is some compression applied to the audio, so sound quality is arguably slightly lower than a standard CD.

Formats such as DVD-Audio and Super Audio CD, launched a few years later, could also offer surround sound and meant an end to the DTS 5.1 Music Disc, though several hundred titles were released on the format.

DTS surround sound technology is also used in movie theatres, on DVD-Video and on Blu-ray. It was also used on a small number of LaserDiscs.

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QSound Compact Disc (1991 – 2001)

QSound is an audio processing system introduced by QSound Labs. It was applied at the sound mixing stage and attempts to produce a surround sound effect from a stereophonic source. It was used on around 65 Compact Disc albums from 1991 to around 2001, which display the QSound logo. The first album to use QSound was Madonna’s ‘The Immaculate Collection’ and all the tracks were either re-mixed or mixed using the system.

No additional equipment was necessary to play a QSound Compact Disc, and the discs comply fully with Red Book standards.

As well as Compact Disc albums, the QSound technology was also applied to computer game audio, television programmes and film soundtracks.

On mono devices, music mixed using the QSound system can have elements missing.

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SQ Quadraphonic (1971 – 1979)

SQ Quadraphonic (from ‘Stereo Quadraphonic’) was a system for providing quadraphonic sound from four speakers on vinyl records. It was introduced by CBS Records in 1971, and was adopted by a number of other record companies including EMI and Sony.

It was a matrix format, so the four channels were encoded into the stereo grooves of a 12-inch LP and then decoded back to four channels. As the grooves were slightly broader than a standard LP, playing time on an SQ record was reduced.

Of the different quadraphonic systems for vinyl, SQ has the largest discography and this was partly because SQ records were fully compatible with stereo equipment. Some early Compact Discs still used the SQ mix.

Consumers needed to buy an SQ decoder to take advantage of quadraphonic sound, but early versions provided poor separation. The sound separation of the SQ system was greatly improved by the introduction of SQ Full Logic decoding in 1975, but by this time all quadraphonic systems were declining in popularity and by the end of the 1970s, virtually no SQ Quadraphonic LPs were being released.

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DVD-Audio (2000 – )

DVD-Audio (DVD-A) is an optical disc format for high resolution audio on DVD, and was first introduced in 2000 by the DVD Forum.

DVD-Audio competed with Super Audio CD (SACD), and like SACD could provide longer playing time, far higher audio quality and more channels (such as for surround sound).

Like other DVD discs, DVD-Audio discs can have multiple layers, and can contain both DVD-Video and DVD-Audio content.

Only some major labels have released albums on DVD-Audio, and the number of releases is very small compared to Compact Disc.

Quadraphonic Sound (QS) (1972 – 1978)

Quadraphonic Sound (QS) was developed at Sansui and introduced in 1972. It is a matrix format for quadraphonic sounds from the 12-inch LP vinyl record. It was also referred to as Regular Matrix (RM).

The format was freely licensed to record companies, and was used by a number of them. It offered excellent diagonal separation and was compatible with stereo systems.

Some systems were compatible with both QS and SQ formats, and QS was compatible with the original EV format, and can synthesise quadraphonic sound from standard stereo records.

The tracks on the QS vinyl LP are the same width as standard stereo tracks, so playing time is the same as conventional 12-inch LPs.

The last adverts for QS systems appeared in 1978.

CD-4 (Compatible Discrete 4) / Quadradisc (1972 – 1979)

Compatible Discrete 4 (CD-4) or Quadradisc was a 12-inch LP format created by JVC and RCA and introduced in 1972.

It was the only fully discrete quadraphonic phonograph record system to gain major industry acceptance.

In the CD-4 system, each of the two main channels contained the sum of the front and back signals. A separate carrier was recorded onto each groove wall that contained the difference signal for that side. From this, the combined  signals for each side could be resolved into two separate signals, creating discrete quadraphonic playback. CD-4 LPs could be played on stereo turntables,

The grooves on a CD-4 record are broader than on conventional stereo LPs, so the maximum playing time is reduced, and it was recommended that consumers play CD-4 records with a special ‘Shibata’ stylus, which increased the surface area of the stylus, thus decreasing the pressure on the grooves.

Most of the CD-4 releases by RCA were in the period between 1972 and 1975, with only 11 releases in 1976 and the last release in 1979.

Quadraphonic 8-Track (Q8) (1970 – 1978)

Quadraphonic 8-Track (also know as Quad-8 or Q8) was a discrete 4-channel magnetic tape cartridge system introduced by RCA Records in 1970.

It was based on the 8-Track cartridge, and cartridges were almost identical except for a small sensing notch in the upper left corner of the cartridge. This signalled a quadraphonic 8-Track player to combine the odd tracks as audio channels for the first program, and the even tracks as channels for the second program. The format was not fully compatible with stereo or mono 8-Track players – although quadraphonic players would play stereo 8-tracks, playing quadraphonic tapes on stereo players results in hearing only half the channels at a time.

Q8 cartridges had two ‘sides’ whereas 8-Tracks has four sides or programmes. To compensate for the reduction in programmes due to the doubling of tracks, Q8s used thinner tape to try and increase playing time.

Around 200 different Q8 titles were available in mid 1972. Blank media was also available for home recording.

The last release in the quadraphonic 8-track format was in 1978, although most had stopped appearing by the end of 1976.

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Quadraphonic open reel tape (Q4) (1969 – mid 1970s)

Quadraphonic open reel tape (Q4) was first introduced by Vanguard Records in 1969, and was only ever available in the US market.

It used ¼-inch tape, playing at a speed of 7½ inches per second, and had 4 fully discrete tracks with full-bandwidth (unlike Q8 cartridges which had limited dynamic range).

Like other quadraphonic formats, it was unsuccessful and had disappeared by the late 1970s.

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