SPOILERS IN THE DESCRIPTION, OBVIOUSLY

Nnriek giving Khayrat lessons in playing the Rivaan. It can't play anymore, of course, but that doesn't mean it can't show him how to hold his hands correctly.
So... post-exaltation mother/son bonding sessions?
Vekksaan was a good mother, but not always there for her son. Ironically, she has more time for him now.

In my headcanon, the angaran Rivaan is played similarly to a theremin. Only it doesn't need an outside source for electricity, instead generating the sounds using an angaran's bioelectric field. Unlike a theremin, it can generate multiple sounds at once.

This was just supposed to be a doodle but I liked the sketch too much so....