yeah, you can do that on a 788... here's an excerpt from the manual:
Pitch
1 Press and hold the PITCH/SSA key for about a
second (see “Key sense time” on page 33) and
release it. The indicator lights and the display
changes:
2 If the PITCH CONTROL section at the
left of the screen is not active (there is no box
around it), press the Ó key to move the cursor
there.
3 Use the dial to change the pitch from -6.0%
to +6.0% in 0.1% steps. If playback is being
carried out while this is done, you will be able
to hear the change.
4 Press the PITCH/SSA key to return to the home
screen and once again to turn off the pitch
change.
NOTE
The above steps can be carried out while playback is
stopped or in operation, but cannot be carried out during
recording. It is also possible to start playback while adjusting
the pitch, but not to start recording at that time.
To use the set pitch When the pitch change
value has been set in the way described above, and
the 788 shows the home screen, simply press the
PITCH/SSA key briefly to turn the indicator on and
to change the pitch.