text: how many key used in major c ?(piano) is that left hand b to right hand a?! is that right ?!?   are you asking how many keys on a piano? there are 88. on the left side, the last note (lowest) is a a on the right side (highest), it is a c.  if you are asking how many pitches in the c major scale, the pitches are: c, d, e, f, g, a, b and c (octave above). on the entire piano, all the white keys are in c major.