Some pitch pipes are intended for tuning string instruments, and only provide reeds for notes appropriate to a particular instrument. Chromatic pitch pipes are favored by "a cappella" singers and timpanists. Chromatic pipes most often provide thirteen pitches, each a half step above the previous. By providing all of the notes of a single octave, a singer can start in any key called for in Western music. Different pipes are available for bass and treble voices due to variations in vocal range. Most male and female performers prefer to use F-F pipes and C-C pipes, respectively. However, it is particularly notable that the Men's pipe in F is pitched higher than the Women's C pipe. Pipes in other keys are available, but are much more rare.