Real Time Change Tempo, want to change the speed of music in real time Options

[James Dawson]

Anybody know of software that can change the speed of the music in real time?
What I mean by this is not to load it into audacity, change the speed and then save as "music-5" for say 5% slower etc
Want at least plus or minus 10 percent but preferably plus or minus 20 percent
Do not care about the pitch changing as this purpose is for dancers to change music to the correct speed for practicing or learning new steps or competitions etc
Of course retaining pitch is even better but not essential
Thanks

[lepetitmartien]

Quicktime has for years a tool for time stretching in real time, it's hidden in the developer tools… (install Xcode)