How would I solve the Twins Riddle in Qasir Al-Wasat?

Question

In Qasir Al-Wasat: A Night in-Between, I have solved the Twins Riddle by sheer luck. I'm trying to understand how the solution makes sense. There are several colored pressure plates and I can activate three of them simultaneously. How does the solution make sense? How can I solve the riddle without resorting to trying three pressure plates at random?

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I am not the only one on the Internet. See for instance this forum post:

Similarly, I 'solved' the Twin Riddle entirely by accident, though I imagine there's some sort of way to tell what its solution is meant to be through in-game materials.

or this forum post:

But the twins riddle I only solved by chance (I tried to interpret the riddle, for instance the starting letters of every sentence, but couldn't find any solution that way).

Answer 1

A hint:

It's a puzzle about harmony and not melody.

The solution:

The important thing about the riddle is the information that they should sing the same thing. And by beautiful tune it means a good sounding chord, so if you try something dissonant it won't work. Either way, you should have them singing the same chord. Every tonic, third and fifth will do. There's also a combination of tonic, second and fifth that will do (and have a special effect on the lower room) because it's a arabic ethnic progression that also sounds good (and it's more on the mood of the game).

References: here and there.