I’m making an acapella for the song 'I bet my life" by Imagine Dragons and i am trying to use the “phase cancellation” method. I have an instrumental and the regular but i cannot seem to line the two up so when i invert it it does nothing to the audio. Can someone please give me tips for lining the waveforms together or can someone please make me an acapella ( i would prefer tips so the next time i try i can follow your instructuons) Thank You
If they’re both internet download MP3, they’re not the same. They may sound the same, but MP3 rearranges tones slightly to make the files smaller, and it does it differently depending on the content.
You can use the Time Shift Tool (two sideways black arrows) to push one track earlier and later with respect to the other. If you can get them to cancel at all, you can then use the Effect > Change tools to make one slightly longer or shorter in hopes of getting canceling over the whole song.
But don’t make any commitments on getting it to work.
Koz
Thank you so much but if I were to not use mp3 what should I use? The original? because I have not seen imagine dragons release an instrumental version of the song. I will try the method you told me but it seems that it will not happen but thank you anyways!
Thank you so much but if I were to not use mp3 what should I use? The original?
The bottom like is - It can’t be done! 
because I have not seen imagine dragons release an instrumental version of the song.
If you had the exact copy of the same recording before the vocals were mixed-in, and if there were no effects or adjustments after the vocals were mixed-in, it could be done. But, if you had access to these original recordings, you’d probably also have access to the vocal-only tracks already.
A couple of examples… Let’s say you have in instrumental, and you record a vocal track of yourself singing-along. (You’d have to use headphones to listen to the mixed vocals & backing track without picking-up the instrumentals in the mic.) Or, you could record yourself speaking over background music. You can mix the instruments & vocals, and since you have the exact-original vocals, they can be perfectly subtracted-out, leaving just the instrumental background. You have to be careful of clipping (overload distortion) during mixing if you want to perfectly subtract-out the vocals, but it works.
This can also work if you mix two totally different songs together (say, you mix Beat It and Billie Jean together). You can later subtract-out either song. If you try this, reduce the volume of both tracks by -6dB before you start to prevent clipping.
However, if you record yourself singing the same song twice (or record yourself saying “Hello” twice), these two recordings are totally different at the sample/byte level, and subtraction won’t work at all. In fact, subtraction will sound exactly like addition (like normal mixing).