Now this is a marriage proposal that will make your heart sing.

Earlier this month, Alex took his girlfriend Anna to the University of Southern California, their alma mater, to watch an a cappella show -- but that wasn't all he had in store.

During the finale, Alex and Anna got called up on stage (this was all planned beforehand, of course) where they were serenaded by some very talented USC students. At one point, Alex grabbed the mic to belt out tunes like Frankie Valli's "Can't Take My Eyes Off You," Jackie Wilson's "Higher And Higher" and finally "Your Song" by Elton John before getting down on bended knee.

"The hardest part ended up being keeping all of the coordinating and practicing I was doing a secret from her, but I was able to get all the way to the event without blowing it," Alex told proposal site HowHeAsked. "The night of, with a knot in my stomach, sweating hands and a dry throat, they called us up onto the stage... and the rest is history."

Watch the super sweet video above.