Along the lines of a tool to help learn songs from - - I use my iPHONE and an app called iLIFT - - it allows me to grab the songs from my iTunes library and inport them. Then I can adjust the pitch to match my guitar ( Eb ), this is a great feature as now I no longer need different tuned guitars based on different songs. Bands like Metalica, ACDC or Quiet Riot who's recordings end up being inbetween tunings now can be adjusted spot on.
I play through my phone into just about anything that will take it ( direct to a mixing board, headphones, Computer speakers ) it's all about learning.
For those who work with a singer that needs to find a vocal range they sounds good in, this adjustment of pitch is.....key
Like most tools out there, it also allows ya to set up loops.
Speed can be controlled too....
Anyway - it's a great tool. One of a million out there