Jon Miller wrote in MMDigest 990123:

> It seems that whenever I listen to piano rolls, be it live,
> recorded, or MIDI-ized, ... very fast runs... never are quite even
> in attack and length.  I doubt that even the finest pianist could ...
> play a run this way, so that leaves some other factor. Anyone know?

Jon,  I think this effect is due to two causes: one from the player,
the other from the editor of the roll or MIDI file.  "Hand-played"
rolls are often performed at slower tempos than they are at play-back.
The player (at the original performance/cutting of the roll or MIDI
file), while slowing down the general piece, failed to slow down glis-
sandos (raking across the white notes), or other fast "runs" enough to
match the tempo of the rest of piece.

It is difficult to play fast runs slowly in a natural way, in a way
that retains an organic sounding rhythm.  When the rolls/files are
played back, they sound unnaturally fast or choppy or jerky.  An
example familiar to me is in Eubie Blake's rolls, when he uses his
trademark ascending 4-5 note chromatic riff.  They sound like a
whistle, and don't quite match the rest of the piece.

Cutting rolls at slower tempos, however, means less editing to correct
wrong notes, or even a spoiled rhythm, which brings me to the second
cause of herky-jerkyness: For most of a pop song in 2/4 or 4/4 time,
the editor can easily "quantize" rhythm (usually meaning, to make the
beats come out perfectly on the 2, or 4 beat) in ways appropriate to
either rolls or MIDI.  An example is that a chord, although originally
played splayed, that is, with each of the notes struck at a slightly
different time, is edited to reproduce as if the chord were struck with
all the notes at the exact same time.

But fast runs are not so easily editable.  Nevertheless, the editor,
for business reasons no doubt, tries to correct wrong notes or missing
notes in a fast run and tampers with the original player's performance.
The result sticks out like a bad nose job.

The problem usually lies in the editor ruining the player's original
rubato.  Rubato is a natural "breathing" of the rhythm, both slowing
and speeding, a bit before or after the beat, and hopefully (especially
if it's a dance rhythm!) almost imperceptibly, but just enough to
prevent a certain entropy (decaying energy) which comes from a too-
perfect rhythm.  It is difficult or impossible to add rubato to fast
runs, and therefore, despite much doctoring, they sound unnatural.

Hope this was helpful (it was to me!).  I'm interested in others'
input.

regards,

Johnny Lite