Recording affords players an ability to record performances as they happen. Music can be mechanically transcribed as it is created, as opposed the traditional method of transcribing it at a later date from memory.
The performance is a spontaneous composition

The modern composition studio, with the ability to fix sounds on materials for manipulation and playback has afforded the composer tools to enter the realm of the plastic arts. Direct, physical control of sound making tools is now as much the territory of the composer as has always been the player. Composition includes performance.

In some cases, composers have ceased writing for performers, and many performers have ceased reading music. The differences between performers and composers is being redefined. Specialisms still exist, but often towards different purposes.

The Materiality of Sound