33 RPM is an application that was designed to help you learn a piece of music. The app can adjust the speed and the pitch of the song. This is apparently how musicians would learn to play a song in the past. The digital age makes this task a lot easier. You can simply load a file on 33 RPM and adjust the sliders on one of the control panels to adjust the pitch, speed and volume of the song. The great thing about the app is that it lets you change the values independently.
When you load a file, three different panes and a player will come up. The player lets you control the playback of the file (play, pause, stop, etc). There is an information pane that displays information about your song, like title, artist, duration, file size and format. The bottom pane lets you loop a selection of the song that is loaded. This becomes particularly useful after you have adjusted the speed of a song. If you want to systematically learn the song part by part, you can loop parts of it in a slow speed. I don't think there is a better way to learn a song than that.
In short, if you want to learn to play a song, 33 RPM has nice tools that can help you with that task. The trial version lets you test the app fully before you have to buy it.