.. How do I solve the little box with the triangles?

To the left of the table, there's what looks like a tea trolley full of hourglasses. On the bottom shelf, there's a small box with some triangles on it. When you pick it up, Nancy says she needs to get all the triangles pressed down. Read to the end of this hint for a quick way to do this.

Play about with it a bit, and you'll soon discover that each triangle also affects every other triangle that it shares a side with.

This kind of puzzle sends me around in circles. The way to avoid this is to think ahead, something I'm very bad at.

For example, if A affects B and C, press whatever pieces you need to get B and C up, so that when you press A all three will go down. See?

If you mess with this for half an hour and start screaming at the screen, press the reset button, then press the pieces in this order:

Triangle Box

Inside, you find some sweet (ish) letters between Magnus and Elisabet. He repeatedly asks to borrow her grandmother's langspil, which is a musical instrument of some kind. Say, didn't we see a bunch of instruments in the Missti Skip?

What am I doing with the musical instruments in the pub?