This is an amazing first submission! You did well with putting the movie to the music, and you were able to make the shapes move in as logical a way as shapes could walk :)
The guitar part was interesting, but if you want a personal opinion, if you had a star or something with two appendages aiming out of it, you could feasibly have that hold and seemingly play the guitar. A triangle works in all honesty, just as a music student, I would think a star would be more apt to play guitar.
But this is fine as is! Keep up the good work!