What do you guys do when you want to figure out the intervals of a song but a certain riff or segment is played fast? I can differentiate intervals decently when they are moderate placed but the second a riff gets kind of fast like 3 or 4 notes a second I cant make them out. Do you guys just slow the song down?
That's a pretty normal problem. Even if you can't get the exact intervals/melody, you can narrow the options by listening for big vs small intervals, high points and low points, overall feel, first note/last note. Just try to get as much information as you can and go from there.