https://www.wired.co.uk/article/musicians-synch-brain-waves
TL;DR: Musicians brainwaves sync up.
So when the Final Five were hearing that music, they were syncing their brainwaves, creating that music in their robotic communications to each other. When they did this, they were able to access information. We see them do something similar near the final episode went they're syncing up to recover the information of resurrection.
So the music wasn't a trigger. It was them communicating with each other on a purely brainwave level.
It was great sci-fi.
and
The ending meh, but overall very good.