Charles Rosen reviews Robert Philip’s Performing Music in the Age of Recording in Playing Music: The Lost Freedom:
His main thesis is that recording has directed performance style into a search for greater precision and perfection, with a consequent loss of spontaneity and warmth. Various expressive devices once common in the early twentieth century have been almost outlawed: ‘portamento’ (sliding from one note to another on a stringed instrument); playing the piano with the hands not quite together (Philip calls this dislocation); arpeggiating chords (not playing all the notes of the chord at the same time but one after another), and flexibility of tempo.
Why?
When a recording is intended to be a renewable image of the music rather than the capture of an individual performance, then even eccentric details become less desirable. A sudden rhythmic hurrying of the second theme by Schnabel in Mozart’s Concerto in C Major, K. 467, was interesting and effective when I first heard it; now I wait for it come and it is an irritant.