Progressive rock can be both challenging and accessible, much like a James Joyce pop-up book or a mathematical proof written in barbecue sauce. Calculate the thrills of the incalculably catchy with today’s Groupon to see Yes and Styx on Monday, July 11, at 7 p.m. at Nikon at Jones Beach Theater in Wantagh. Doors open at 6 p.m., and parking is included. Choose between the following options:

• For $20, you get a ticket for seating in section 8L, 8R, 10L, 10R, 12L, 12R, or 14L (a $29 value before fees, or up to a $39.50 value online, including all ticketing fees).
• For $31, you get a ticket for seating in section 11L, 11R, 13L, 13R, or 15 (a $49 value before fees, or up to a $62 value online, including all ticketing fees).

Having helped shape the rock landscape, Yes and Styx continue to flex their honed and toned musical muscles as they co-headline their 2011 U.S. Progressive Tour. The virtuosos of Yes flaunt their titanic talents as they crack the spine on a songbook that includes showstoppers such as “Roundabout” and “Owner of a Lonely Heart,” as well as material from their newest album, Fly From Here. Styx, responsible for tunes such as “Come Sail Away” and named for the most popular water park in ancient Greece, invites listeners to hitch their ears to its litany of hits, many of which have been re-recorded for the band's Regeneration series.