The idea of the "rock opera," as most folks know it, started with the Pretty Things and their album "S.F. Sorrow" in 1968. The Who quickly followed with "Tommy," arguably the most highly regarded rock opera of all time, and the race was on. The Who also recorded their "Quadrophenia," and Pink Floyd's "The Wall," David Bowie's "The Rise and Fall of Ziggy Stardust," The Kinks' "Arthur," "The Lamb Lies Down On Broadway" by Genesis, Green Day's "American Idiot," the Drive-By Truckers' "Southern Rock Opera" and My Chemical Romance's "The Black Parade" are a representative few that prove the form has sustained ongoing momentum over time.

Oh, and don't forget Meat Loaf's "Bat Out of Hell," which is far and away the most successful rock opera ever.

But the Trans-Siberian Orchestra is perhaps the only rock act that formed specifically to make and tour behind nothing BUT rock operas. They're written and recorded 312 so far and, in fact, the Oxford English Dictionary is considering adding another syllable to the word "libretto" to give it more heft and heaviness — all because of the Trans-Siberian Orchestra!

In any event, the TSO returns to Mohegan Sun Sunday for their traditional holiday appearance in the Arena. This time out, they're performing a 25th anniversary version of their popular "Christmas Eve and Other Stories" production. Jolly has never been so marvelously grandiose!

Trans-Siberian Orchestra, 8 p.m. Sunday, Mohegan Sun Arena; $50.50-$89.50; www.mohegansun.com.