hi how do u tune a saxaphone?
also wot is the spit valve for?

spit valves are on brass instruments, not sax. You blow, and the spit comes out. Tuning. loosen mouth/embuchure to flatten, or pull the mouthpiece OUT. To sharpen, push in or tighten mouth/E. (this is harder)

bari saxes and basses (if you run across one) have a spit valve in the at the bottom of their "loop" in the neck, and its just to empty to the spit that builds up there, hence the name. You could also be mistaking the octave key for a spit valve too, i suppose.