sega has emulated the sega saturn but won't share
Nights uses more customized audio synth drivers, and makes full usage of reverb/sound buffer effects effects to make the music play smooth (as example, when it plays a note, and stop playing it, the sound won't stop right away, it'll be gradually cleared form the soundbuffer, so when it plays the music tracks, you don't notice gaps between each tone).
AFAIK, the current GiriGiri doesn't emulate the sound buffer effects that much, so the synth music in all games is supposed to be much more midi-ish, when it doesn't happens to go insane (Radiant Silvergun music goes crazy sometimes).
Panzer Dragoon Saga music runs without glitches (speed aside, since I can't get full speed in my setup), other the the fact the smooth transitions between notes is missing. GiriGiri at least emulates pitch/tempo changing, that is the basis for PDS music (you can also see it in effect by holding either L or R during the cutscenes and dialogues - L playes them in slow motion, and R doubles the speed, and the voices will distort too, playing slower/faster).