Need some Help!

Hi there, I’m starting using grasshopper since few weeks for the university. I’m trying to make a lid of a kettle with on top of it some pipes/ organ pipes. Every pipe corresponds to a note and every pipe has a specific length A=75 mm, B=140 mm etc. I need to find a way to have the possibility to choose if the pipe is on the lid or not. I need to have a sort of note “NO” where the pipe disappears.
I’ve tried to do it but the pipe refolds.
My English is horrible, hope to be more clear with some photos.

Here are the notes in Italian (DO, RE, MI etc)