Look very nice, I may end up using for https://museeks.io, gapless playback has been on the roadmap for a while, but WebAudio APIs have always been super cryptic, a higher-level API is very much welcome.
To me, the best feature is Relay Fragments (I think Apollo has fragments too?), as each component describes the data they need: no need to do a big top-level request then pass down the data to the responsible components, everything is in one file.
It makes UI changes much much easier to deal with.