rt_pvc is a:

• real-time phase vocoder library for synthesis/analysis
• vocoder application that allows the user to do time-expansion, frequency expansion, and cross-synthesis in real-time, from mic-input or from file.
• real-time phase vocoder visualization
• learning tool that teaches about the phase vocoder and its implementation
• open source!

soundlab.cs.princeton.edu/software/rt_pvc
aur.archlinux.org/packages/rt_pvc