Introduce one musical intrument at a time. Place the musical instrument in a mystery box. Invite students to come up, one at a time and describe what they feel in the box, not tell what it is.
They can be encouraged to use words like: hard, metal, wood, smooth,ect. I usually start with the cymbals. Have enough instruments on hand for several students to be able to play them at a time. While they are playing the instrument, have the other students say the name of the shape if a funny voice. Give directions about how many times to play the istrument.
Continue to introduce an instrument a day:
sand blocks- rectangle
wooden blocks (from block center)-square
bells- diamond (this is a stretch, I know, but
when I think of bells, I think of ring, ring, I think of diamond)...the kids love it!
On sentence strip, you can cut out shapes and allow the students to read "shape" music. This can be left out for a center if you can stand the noise!
I always allow time for "all play"!