The ManningCast turned into a full-blown concert during "Monday Night Football" ... with Peyton and Eli Manning singing their hearts out -- and Tua Tagovailoa providing the tunes!!
The Miami Dolphins quarterback put his music skills on display as the Cincinnati Bengals and Jacksonville Jaguars duked it out on national television ... strumming the notes to Eric Clapton's "Tears In Heaven" as the Manning brothers crooned their play-by-play.