If Rousing Refrain is in your hand, cast it by paying 3.
Otherwise, activate The Tenth Doctor by paying 7, causing you to time travel three times, removing all time counters from Rousing Refrain and cast Rousing Refrain from exile without paying its mana cost.
Resolve Rousing Refrain, adding at least seven , and exiling Rousing Refrain with three time counters on it.
Repeat from step 2.
If an opponent has eight or more cards in hand, this combo nets infinite red mana.
This loop hinges on accelerating suspended spells to create an unstoppable engine of resources. By activating The Tenth Doctor's hefty time travel ability, you immediately strip away all three time counters from Rousing Refrain and cast it for free straight from exile. Once Rousing Refrain resolves, it refills your mana pool based on an opponent's hand size while naturally exiling itself back into suspension with a fresh set of three time counters, perfectly primed for the Doctor to pluck them off again.