on song

prepositional phrase1

1. •
   (UK, informal) Playing or performing well.

   • Alex (not on) Song as ITV pundit in Berlin -- West Ham's former Barcelona player endured a tough evening in ITV's Champions League final studio. https://uk.eurosport.yahoo.com/blogs/world-of-sport/alex--not-on--song-as-itv-pundit-192922810.html