Slow Down Music Trainer 4+

It's quite amazing what MT 2.1 does for just a couple of bucks, considering you can pay several hundred bucks for a Tascam slow downer device and around fifty for some of the current computer-bound guitar/riff/song software packages. Those products do a lot of other functions, too, but the fundamental and most desirable feature for learning songs with any of these programs or devices is the ability to slow the songs down significantly without introducing noise artifacts. MT does that quite well and you can change key easily too.
Some reviewers have complained that it's not so easy to enter songs into MT 'directly' from your IPhone. But how you do this is basically just like adding a song to an ITunes playllist: go to a web site, upload the song via an "upload" (browse) button, and then ITunes syncs it into MT. I'll be interested to see if even more features are added to later versions, but I'm very impressed with MT 2.1 and still find it hard to believe I got it for just a couple of dollars.

Still great after using it for 7 years!

The app seems to work well so far.
Only issue is the app struggles with variable bit rate mps files. It only shows 0 to 23 seconds of the song at a time and is pretty much impossible to select a phrase from variable bit MP3 song. I was able to slow down an speed up but unable to choose a phrase to loop over.
So works well with fixed bit rate but not variable bit rate encoded MP3 files.

This is a great app if you’re trying to learn a new song and want to play along with a professional recording. It’s very helpful to be able to slow the song down and be able to play and replay certain parts. Until you’re happy with it. It’s helped me progress with more difficult pieces.