Starting in the mid 1940s, recording became understood as a technique for music production as well as merely reproducing pre-existing music. An early pracitioner[Schaeffer 66] listed three potentialities of the new medium: permanence (the ability to fetch a sound later that one had made previously); reproducibility (the fact that, of you have one copy of a sound you can have as many others as you like), and reversibility (the fact that you can play the sound backward; today, we would generalize this to say “manipulability”).
In the digital era, every sound that is manipulated is first recorded in order to get it into the computer, even if it is then used and erased within a few milliseconds. Recorded sounds are streams of numbers, and manipulations on them are described by mathematical formulas.
[Schaeffer 66] Traité des Objets Musicaux, Paris, Éditions Du Seuil,1966.
Available in English translation.