Thanks for making this, it's wonderful and will make a _huge_ difference to my listening on Spotify. For example, I've got a thing about Ravel's Piano Concerto in G and I've found a whole load of new recordings I knew nothing about. A few comments and suggestions:
Pieces are sorted strictly alphabetically, which means that lists of "String Quartet number X" are sorted like:
String Quartet no. 1
String Quartet no. 10
String Quartet no. 12
String Quartet no. 13
String Quartet no. 2
Not sure how complicated that is to change, but it would make browsing a little easier if they were listed numerically.
I find the horizontal listing of composers a bit unintuitive, and would prefer a vertical list (probably to do with ubiquity of vertical scrolling in apps and browsers), perhaps between favourites and list of works. Really like the fact that it includes images and isn't just a dry list of names though.
Seems like there are a number of not-so-esoteric composers missing, such as John Luther Adams (a different person from John Adams), Gavin Bryars, Jacques Duphly and Gérard Grisey, despite the presence of composers that I'd never heard of like Orlande de Lassus. I guess this is a limitation of the data sources, but would love to see some more of those included too.
Searching for "Jana" doesn't return Janáček - presumably because of the accents. Would be great to ignore accents for easy typing on British English / American English keyboards.
The small application icon on Mac - for example the installer disk image icon, and the icon in Mac notifications, is a frazzled multicoloured square rather than a proper icon.
Sometimes a message comes up saying "This isn't available on Spotify - bummer!" but doesn't explain why. I didn't think to check when it happened, but I guess it might be that it's not available in my territory (the UK), and I have Spotify set to show tracks that aren't available. If there was a way to have a bit more explanation in that error message somehow that would be helpful - for example, if it's to do with my setting to show tracks that aren't available, a sentence to say that toggling that setting would make that not happen.
A tiny, tiny thing - clicking Apple + A when in the search box doesn't select all text although double-clicking does.