Why can't I use master tempo/key lock or effects on my CD player?

Serato DJ interprets the signal coming out of the CD player, and uses this information to control the play back of the files on your computer. 

Any audio processing performed on the signal before it reaches the hardware interface, such as key correction, will scramble the signal making it illegible to Serato DJ.

Do not use the master tempo/key lock on your CD player if you are using control tone CDs to control Serato DJ.