Here is an essential shoulder exercise for musicians. It will get you started strengthening the very important (but often ignored) muscles on the front of the shoulder blade.
Purpose: Shoulder blade strength and control
Tempo: 1-2 seconds up. 3-4 seconds down
Perform 3 rounds of 8-12 repetitions 3 days per week
Tip: Try not to let your elbows flare out or lift off the wall.
If it’s too hard: Don’t slide all the way up.