I believe there are certain composers using not a 12 tone system, but a system with more pitches in one octave. This is very experimental, but it'd need a way different notation, and can only be played on electronical instruments, as far as I know. Don't ask me what it sounds like, I've just read about it.
But the Cello Concerto!!! That's another story!! In the strings he has them playing half-sharps and flats (quarter tones) throughout!!! I was going to make a piano transcription of this piece but it seems quite impossible now!! I COULD use one of the pianos (I plan to use FOUR pianos) tuned a quarter tone too sharp or flat...but...I dunno...Is it too much trouble than it's worth?
In the strings he has them playing half-sharps and flats (quarter tones) throughout!!! I was going to make a piano transcription of this piece but it seems quite impossible now!! I COULD use one of the pianos (I plan to use FOUR pianos) tuned a quarter tone too sharp or flat...but...I dunno...
bartok also uses quarter tones, and quite frequently.about re-tuning the instrument, for strings it's not an uncommon practice - it's called "scordatura"