I have a restriction for this: the time duration of the sample cannot be changed, because I need to use input from the microphone and play it back asap. This means pitch shifting via playing it back at a different sample rate is not permitted.
 More info: I'm looking for various kinds of filters to apply to voice input from the microphone. I've tried some amount of pitch shifting, however, I'm not sure of the direction that I should move from. Also, I can't control the setup; this conversion has to work out of the box through a program and a microphone.