Change Tempos & Keys With Amazing Slow Downer (ASD)
I often get asked if it possible to change the tempo or the key to a Jazzbacks backing track.
The answer is... Yes!
At some point in time, anyone who uses backing tracks for practice or performance is going to want to alter the tempo or change the key of a backing track in order to slow it down, speed it up, or make the key more achievable for their vocal or instrument range.
The good news is that there is an app that will slow down or speed up the tempo, or change the pitch (the key), without loosing too much of the original quality of the track.
Amazing Slow Downer (ASD) 
The app is called Amazing Slow Downer and can be found at: www.ronimusic.com
I would like to make it clear at this point that neither I or my website, Jazzbacks, have any affiliation or business interests with this product. I am only writing this because I have found this app to be an extremely useful tool for my personal backing track use.
Amazing Slow Downer is available for Windows and Mac computers as well as Android and iPhone/iPad devices. This article is based on using ASD on my Macbook Pro.
Quality Control
Whenever you the alter pitch or tempo of an audio file you run the risk of losing some audio quality. With the ASD app there are five algorhythm, or 'slow down modes' to choose from. I have found that if one mode has quality issues, another mode can be found that will achieve a much more satisfactory result. I also found that different tracks sounded better using different modes so it's worth experimenting. This doesn't take more than a second to do, by the way, so it is well worth trying for the best result.
Save it for later
Once you have achieved the desired settings you can save the song as a new file (AIFF, MP3, QuickTime, or AAC/MP4 file), or just leave it in the ASD player for your next practice session.
You also have the ability to easily loop a section of the piece to nail a difficult passage, gradually bumping up the tempo until you have it under control.
Work out your favorite riffs.
The benefits of using this app don't stop here. Let's say you are trying to work out a particular Charlie Parker riff that he plays on your favorite recording, but he plays it way too fast for you to figure out the detail. Pop an MP3 file of the record into ASD and slow it down to a tempo where he is playing at a mere mortal's tempo, you'll soon be able to work it out. I even read somewhere on the ASD Roni Music site that you can integrate with your Spotify library, a fairly amazing feat, even in this day and age.