The first major breakthrough in practical stereo sound was made by Bell Laboratories, who in 1937 demonstrated a practical system of two-channel stereo, using dual optical sound tracks on film.

German audio engineers working on magnetic tape are reported to have developed stereo recording by 1943, but it was not until the introduction of the first commercial two-track tape recorders by Ampex in the late 1940s that stereo tape recording became commercially feasible.

A large amount of pop singles were mixed into “monophonic” sound until into the late part of the 60s and although famous albums by bands such as The Beatles Sgt. Pepper's Lonely Hearts Club Band were produced in stereo, it was common for pop releases to be produced in mono and stereo until the early 70s. Many 60’s pop albums now available only in stereo were originally intended to be released only in mono, and the so-called "stereo" version of these albums were created by simply dividing the two tracks of the master tape. In the late 60’s, as stereo became more popular, many mono were re-mastered using the so-called "fake stereo" method, which spread the sound across the stereo field by manipulating the higher-frequency sounds into one channel and the lower-frequency sounds into the other.

Digital Recording

The creation of digital sound recording and the CD in the 80’s revolutionised the durability and overall quality in which we listen to music. The CD initiated another massive wave of change in the consumer music industry, with vinyl records effectively relegated to a small market by the mid 90’s. The most recent and revolutionary developments have been in digital recording, with the invention of purely electronic consumer recording formats such as the WAV digital music file and the compressed file type, the MP3.

This generated a new type of portable digital audio player, the MP3 player. The most popular mp3 players are the Apple iPod. Another invention was the mini disc player developed by Sony, using ATRAC compression on small, cheap, re-writeable discs. This was in vogue in the 90’s, and is still popular, especially in a newer, longer playing and higher fidelity version.

Developments in technology for recording and editing have proven to have improved and transformed the record, movie and television industries in recent decades. Audio editing became practicable with the invention of magnetic tape recording, but the use of computers has made editing operations quicker and simpler to execute, and the use of hard-drives has made recording cheaper.

Multitrack recording makes it possible to capture sound using several microphones, or allowing maximum flexibility in the mixing and mastering stages for editing, level balancing, compressing and limiting, and the addition of extra modifying effects such as reverberation, equalisation, flanging and many more.