Anthony Roth Costanzo is a feisty performer who knows a thing or two about busting down barriers in classical music. After all, opera singers don't normally belt out arias behind office desks, and they don't insist on lugging harpsichords with them. They also don't routinely sing in Bronx middle school classrooms and get students talking about emotions. But Costanzo is fearless. (And after seeing this amazing Tiny Desk performance, watch him melt the hearts of distracted sixth-graders.) A word about Costanzo's voice. He is a countertenor, a man who sings in the range of a female alto. The roots of the tradition date way back to the 1500s, when young male singers, called "castrati," were castrated in order to preserve their high, flexible voices. "I've managed to do it without castration," Costanzo joked to the audience of NPR staffers. These days, countertenors sing in falsetto, and while as recently as 30 years ago it was considered something of an androgynous novelty, now countertenors are part and parcel of the opera world. (We've even hosted a countertenor before at the Tiny Desk.) Costanzo performs songs from his new album, which pairs music by George Frideric Handel with Philip Glass. Strange bedfellows perhaps, and born more than 250 years apart, but somehow Glass' repetitive, staccato beats and Handel's long, flowing melodies manage to shake hands across the centuries. One obvious common thread is the arrangements, by Nicholas DeMaison, that Costanzo commissioned expressly for this performance, featuring harpsichordist Bryan Wagorn (playing a beautiful double-manual French-styled instrument built by Thomas and Barbara Wolf), along with flutist Alice Teyssier and bassoonist Rebekah Heller. Glass' "Liquid Days," begins with a recitative introduction, similar to a Handel aria. But the lyrics, by David Byrne, depict love, in all its quotidian splendor, as a character who "could use a shave" and "watches TV." "Pena tiranna," from Handel's undervalu