Hi there.
I have a question that I hope someone can answer. I have been playing tenor sax for 2 years. Recently, when I played a low 'G', it warbles between high and low G. Does anyone know why that would be?

Most saxophones have an alternating octave key. When holding down the G key, the octave key on the crook drops and the one hidden behind the top Bb key opens. If the crooks on wrong, or if a spring is going, then an octave key can either stick open or stick closed - this is probably what's happening to you

I imagine you have a problem with pads sticking so they don't open / close properly between the low and high G's. I would get it checked out by a specialist.

I have this problem to! Its really annoying! But i havent worked out how to solve it yet.

if you have tried all of your pads and they work try losening your embrouchure. (havent a clue how to spell it)