There is one very effective strategy you can use: ear training with your voice.
If you are working on relative pitch (intervals, scales, chords, chord progressions) then singing through drills is a great way to improve your ears. You can do this out loud by singing or humming, or in your head using audiation.
This is particularly effective if you are using solfège for relative pitch practice, as you can practice singing up and down scales and jumping between notes, improvising melodies. In this way you i