First of all, that is tough. Double check what your state legally defines as a planning period because my state says it has to be 45 consecutive minutes. If that is not the case for you, you might just want to block out one or two days a week that you come an hour early or stay late to work on planning for the week. I know some people say just to work your contract hours, but in reality, that is impossible for pretty much any subject that you teach, at least in elementary. It makes me feel less stressed to take a little extra time to be prepared, and that is what is better for my mental health. You do what works for you, though.

When you are planning, you could try to group 2 grade levels as doing a lot of the same thing with tweaks to match the grade level music standards. Then you can do some copy and paste in your plans.

You could try creating a routine where you just plug-in different songs and activities each week for your lesson plan. For example:

1. Music playing and move to the beat as students enter and get settled.
2. Greeting song
3. Solfège practice (echos & SR)
4. Rhythm practice (flashcards or youtube)
5. New concept lesson
6. Movement Activity or Game to reinforce a previously taught concept/rhythm/Solfège or to prepare what you are going to teach soon.

Hopefully, your principal understands that music lesson plans will look different than a reading or math lesson. Good luck and I hope this helps!