After about 1 month of taking lessons from my teacher(2 1/2 months of playing DB), he has pinpointed my major weakness. I have alot of trouble singing notes, my internal pitch needs lots of work. So he started me practicing at the piano signing root-minor2nd, root-major 2nd and all the way up like that, plus permutations of the major scale. And he also recommended signing to a tuner so I could practice holding one note. Obviously this is very important for playing DB. My question is, does anyone know of any good books & CD's for this kind of problem?