You can detune the pitch of the MIDI instrument assigned to a part using the "Transposition" column inside the Playback Console.
Most transposed instruments listed in Part Name column of the Playback Console have already been preset with to their proper detuned value. Changing the value +24 or -24 will also modify the timbre of the MIDI instrument assigned to that part.
NOTE …
Changing Transposition values in the Playback Console only affects pitch. It does not change the position of the note heads in the music (See Transposition).