It’s amazing how a cappella groups have become headliners over the past few years.

I guess you could trace it to the popularity of “Pitch Perfect” and “Glee,” but whatever the impetus, it’s meant that groups like Pentatonix can draw arenas full of fans.

So it is with Straight No Chaser, an all-male a cappella group that has played the Mohegan Sun Arena before — and will again on Sunday.

The group formed back in 1996 at Indiana University and hit the big time in 2007 when a video recorded in 1998 of their version of “The 12 Days of Christmas” went viral.

They now turn their voices to a wide range of numbers, from “Signed, Sealed, Delivered I’m Yours” to “Lean on Me” to “Seasons of Love.”

Straight No Chaser, 7 p.m. Sunday, Mohegan Sun Arena; $30; mohegansun.com.