How do you make a sound, musical note, be controlled by some attribute, e.g. length, of some object, so that as the length changes, the note changes with it?

I tried using the wave node, and right-clicking on the period property and inserting an expression like "line1.length" (for a line1 defined in a geo node) I get "unable to evaluate expression". How should I proceed?

https://forums.odforce.net/topic/24978-geophone-experimental-animation/#comment-145649 [forums.odforce.net]
this gonna give you Ideas