A system of 7 planets orbiting a dwarf star, many capable of potentially harboring life. One scientist studying this system realized that the planets orbits were stable despite their proximity to each other because their gravitational fields were resonating with each other. With this in mind, he sped their orbits up by orders of magnitude so that each planet’s orbit corresponded to a particular note. Here, then, is what TRAPPIST-1 “sounds like”.
This is a better video from which the first was edited, and includes a little more info about the whole process of getting there.