I use a program called the Amazing Slow Downer. You can slow down recordings keeping the same pitch, you can alter the pitch via semitones or +/- cents for those recordings which are just a few hz out, you can EQ it to try and remove vocals, or bass, or isolate the bass, loop segments over and over to work it out, etc. Really useful program. You get asked to learn a song in a different key? You just load it up, change the pitch up or down by however many semitones you need, and away you go