(this is an archived copy of the original post)
This technique is based on the method used with the very interesting MIT Scratch demo project 'OceansMusicBox'.
In that project, a tall ImageSprite triggers sounds and animation events on seastar ImageSprites which, when dragged on the canvas, change in pitch and time fired.
The music voice for the stars can be changed also.
This was the inspiration for my Piano Composer app:
In this demo project, a tall ImageSprite is made to collide with 4 balls.
Each ball has a CollidedWith and EdgeReached event block.
This results in the balls moving back and forth in unison.

Any blocks that would need to be executed simultaneously could be placed inside the CollidedWith event blocks.
I would like to hear from any of you who can find another use for this technique.
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Scott