Music.app has a lyric-displaying sidebar now, but I made this work out of curiosity to see how stupid the port from iTunes.app to Music.app was. (Answer: medium stupidity.)
They respond to all the same AppleScript messages, just in a different namespace -- in case doubt lingers about it being a lie that iTunes has been "retired" and Music.app is some brand new thing. No. No, they just renamed the app and deleted a bunch of features. I told you so.
Most of the hassle involved silent failures due to moving target sandboxing API whack-a-mole.