Next layer: how can you tag your music files with metadata tuned to the needs of your music player? My suggestion: the MusicBrainz Picard tagging app and the ClassicalExtras plug-in are indispensable. They each have a lot of controls and a lot of documentation. Try to figure out how to make them do what you want, and ask further questions, in new topics, on this forum as required.
Next layer: how can you enter metadata into MusicBrainz in a way which lets the tagger do its work well? My advice: enter the data in the most correct way, using the best MusicBrainz structures you can. Rely on the tagger to transform that data into something your music player can use. Resist the urge to put things into MusicBrainz the wrong way as a hack to get your music player to work.
As Hollander said in another topic,
Artist-Recording relationships are the appropriate MusicBrainz structure for representing singers performing in a track of an opera album. Be diligent about entering singer (and instrumentalist and symphony and conductor) relationships for every recording (“track”). While you are at it, learn about MusicBrainz Works. Be sure that there are Work entities for every opera, and part of an opera, performed in the opera albums you enter. Add appropriate Recording-Work relationships.
As part of this work, you will become good friends with the Classical Style Guide (CSG). It is complex, because classical music metadata is complex. As you have questions, ask them (in new topics, in the MusicBrainz Style) category) in this forum.