https://wccftech.com/ios-12-lets-you-search-songs-on-apple-music-using-lyrics/

If you remember a part of the song, then you can use those partial lyrics to search for a tune in Apple Music in iOS 12.

When it comes to searching for songs in Apple Music, or pretty much any music streaming service out there, you have to be very specific about the artist or song name. But with iOS 12, Apple is diving deep into search by allowing users to search for tunes using nothing but lyric phrases. Keep one thing in mind though: this feature does not work with every single song as some have missing lyrics and iOS 12 is way too early in its lifespan as beta software.