When I’m trying to learn a piece of music with changes that happen too quickly for me to identify the details, I slow the tempo of the song to a point where it’s possible for me to do that. Slowing the tempo does not affect the pitch, which is important if you want to learn in the key of the original.

This explains how to change tempo in Audacity, a free cross-platform audio editor.

Import the song

Get a copy of the song in almost any common format. This will often be an mp3 but whatever you use, Audacity has to be able to import it.

Once you have the file:

1. Open Audacity.
2. Select File -> Import -> Audio.
3. Browse to the audio file.
4. Open it. The song will load into the Audacity editor.

Copy the section of interest

1. Add a new track: Track -> Add New -> Stereo (or Mono as appropriate).
2. If you want to slow down the whole song, you can Select -> All; I do this to have one copy of the original untouched.
3. If you want a section, click and drag over the desired area and copy.
4. Go to the new track and put the cursor where you want the copy to go. Paste the copy.
5. Highlight the copy.

Change the tempo

1. Select Effect -> Change Tempo.
2. Tempo can be changed in a number of ways. For this example, use Percent Change. A positive number will speed up the tempo, a negative number will slow it down. Enter -20%.
3. Click OK. The section will expand on the time line.

Play the expanded section; it will be slower than the original but at the same pitch.