Thanks @joel for your understanding. The sort by “performance popularity” does not help find the complete composition, at least in the case of Qobuz’ 1107 results for the Matthew Passion - the whole work still appears mixed up with many different arias or excerpts.
If you can’t identify complete compositions from the metadata - something that may indeed be tricky with classical because of variant performances - can I suggest using the duration. It seems pretty obvious to me. A big piece like the Matthew Passion or an opera is of the order of two and a half hours long; individual arias from it are a few minutes. A symphony or concerto is typically 20 - 40 minutes; an movement a quarter of that. So if there was a way of filtering or sorting by duration that would probably give a good result. Your search results already show duration, so you must be able to exploit it. What does not make sense at the moment is that you quite correctly describe the Mathew Passion as having 108 Parts/Movements but then show a single aria lasting less than a minute. At 4 or 5 performances per iPad screen, 1107 possibilities is 200 screensful …