How to quickly temporarily change speed of playback?
 
Need to temporarily change play speed for testing tempos of different sections.
 
Sixteen audio tracks.
 
 

For individual tracks slip stretch or shrink to desired length. Play song. Hit Ctrl+Z to undo and repeat as needed.
 
For entire song slip stretch or shrink all tracks to desired length. Play song. Hit Ctrl+Z to undo and repeat as needed.
 
Last one works best when all tracks contain single clips of equal lengths and they all begin and end at the same position.