AudioScrub is described as 'Slow down music, change the key, and loop' and is an app in the Education & Reference category. There are more than 10 alternatives to AudioScrub for a variety of platforms, including Windows, Mac, Linux, iPhone and iPad. The best alternative is Transcribe!. It's not free, so if you're looking for a free alternative, you could try Amazing Slow Downer or PaulStretch. Other great apps like AudioScrub are Capo (Paid), MusicTrans (Paid), BestPractice (Free, Open Source) and Audioalter (Free).
The SPT-667 Phrase Trainer makes learning riffs by ear really simple. Say you want to copy a guitar solo. The Phrase Trainer lets you to load the song (wav,mp3,wma etc...) slow down the playback speed to as little as 50% (or speed it up to double-speed,why not?
Audio slow downer that changes key and/or tempo. Allows for the isolation of multiple Audio Segments (loops) within a single file. Apply different keys, tempos or EQ’s to each loop. Also contains automatic key, tempo and chord detection.