Yamaha DTXpress/DTXplorer/DTXtreme

Tuning native voices allows increments of 1.17 cents (Tune Fine 
setting).  Perhaps I'm missing something, but tuning MIDI voices only 
allows half step increments it seems.  Do I have to use some external 
computer/keyboard to get greater control of pitch for MIDI?

The case where this came up was I was using the MIDI "tubular bell" 
setting for chimes in a show, when the Music Director suggested that 
the intonation wasn't quite on.  We ended up cutting the part because 
I couldn't get it in tune with the keyboard.

Thanks in advance,

Galen