libsbsms is a library for high quality time and pitch scale modification. It uses octave subband sinusoidal modeling.
The API is found in sbsms.h. sbsms_create is called and supplied a callback which feeds sbsms_process samples. The pitch_create and pitch_process functions are called only if pitch shifting is required. It simply sticks a resampler on the end of the FIFO.
NOTE: When reading the output from sbsms, you must determine a stopping condition for yourself, as the library zero pads the output ad infinitum and never returns 0 samples. The simplest method for doing so is found in test.cpp.
Call './configure && make' on the console to compile the library, Then 'make install'. The latter has to be called as root.