In the 1960s, it took pop and rock groups one or two days to record other their songs. Nowadays, it can take months and months. Many rock groups begin by recording only one instrument, for example, the voice. Then they record other instruments – electric piano, synthesiser, guitars, drums and so on.

Next, they might use a computer to add special effects. Finally, they ‘mix’ all the instruments until they get the sound that they want. This means that a CD or cassette will always sound very different from a live concert.

Music engineers have developed a new eomputer programme that will change the future of music. A computer can analyse a singer's voice. Then if you give the computer the lyrics and music of a song, the computer can 'sing' it in that voice. This means that a singer only needs to record one song and the computer can then sing other songs in the singer's own voice. Singers can sing new songs many years after they have died.

Most of us listen to music for pleasure, but for the record companies, music is a product, the same as soap powder. When a record company finds a new group (or 'band'), they first try to develop the band's 'profile'. They will try to create an 'image' for the band that they think will attract young people. Instead of allowing the band’s full artistic freedom, they will often tell the band what they should wear, what they should say and how they should sing and play.

In recent year, many rock groups have started their own record companies because they say that the big companies are too commercial.