"The bandwidth limitations of the serial Musical
Instrument Digital Interface (MIDI) protocol used by
many control surfaces creates a tradeoff between
responsiveness and the number of controls. With 31.25
Kbit/s MIDI, for example, a maximum of 35 controls
can be controlled in a 33 ms video frame interval
(assuming three byte MIDI commands)."
"In addition to bandwidth limitations, many of the MIDI
protocols have insufficient resolution in their data types,
for example 128 discrete values for a knob, compared
with over a thousand discrete values that might be
necessary for accurately choosing an EQ frequency
value."
original article
here