I recorded a 16 tracks of audio loop from my old keyboard workstation into Sonar prof, 1 track at a time.. at 93BMP.. which was too fast and so i want to slow the tempo down to 91BPM.. without having to record each track again.. I basically copy the loop then edit to make a complete song.
 
Can I stretch all the tracks at once to slow the loop down to 91bpm,  ?   
 
 

Hi. Yes you can.
Right click, and "lasso" the clips so all are selected.
Shift+Ctrl click and drag until it fits.
You might want to turn off snap (N) to get it accurate enough.
All the best.

Then save as a new project in case something goes wrong or you don't like the results.

Q: Would cloning the tracks make it so stretching the 1st one stretches the rest?