Peter Phillips is correct that you can sort of turn off the MIDI delay
on the Disklavier, but it is hardly recommended.  When you set the MIDI
parameter to "Real-time" the delay is reduced somewhat, but it becomes
different for different notes and different velocities, so the result
is a bit of a mess.  Also, the instrument's ability to respond to
quickly repeated notes is severely compromised.

The solution is, as Peter says: advance your Disklavier tracks by 500
milliseconds relative to the rest of the sequence, whether it's MIDI or
audio.  With the delay turned on, the timing accuracy of the Disklavier
is superb, and notes that are "played" at the same time but with
different velocities will sound at the same time, something which would
be impossible without the delay.

Paul Lehrman