Using a fretless.....

Is that what they call playing out of tune these days?

 

Not deliberately. But go check out a Steve Bailey CD; he does it all the time.

 

Try listening to traditional indian music.

 

i mix in quarter tones sometimes...but unless the rest of your band knows what you're doing, you might get some weird looks. thankfully most of my bandmates know indian music and stuff that uses other scales.

 

do you mean equal tempered or just? 24 ET would be easy enough, but any just scale would probably require some markers...

 

you mean like really? Indian music?? but anyway you can always play Indian music on normal guitars and heck even keyboards too