This is a New York City band so unknown that it doesn't yet have a record label: Its music is only available on a mail-order, cheap-quality cassette. But this pop-rock duo is bound for greater glory. John Flansburgh, 26, and John Linnell, 27, write and perform songs that are just wacky and theatrical enough to make them sound unlike any other band. Yet the songs are also conventional enough that anyone can hum along. Flansburgh and Linnell champion the Ogden Nash school of lyric writing; the words are nonsense, yet still a lot of fun. In "Youth Culture Killed My Dog," they sing, "The hip hop and the white funk just blew away my puppy's mind." Another tune is a love ode to a female hotel detective. Some of their 23 very brief songs come across as arty throwaway jokes. But their energetic delivery makes almost any gag work. And if their synthesizer accompaniment sounds not much more complex than the kind of musical doodling any novice can come up with, the beat makes it almost impossible to keep from dancing to numbers like "Put Your Hands Inside the Puppet Head." Linnell also proves that the least hip instruments can make the hippest music as he rocks to several tracks on the accordion and the baritone sax. The Giants, who most often take on a smart-alecky new-wave twang as they sing, show themselves versatile enough to deliver a country song about a cow that lives under the ocean, a hymn about "the day Marvin Gaye and Phil Ochs got married," and an old-fashioned drinking song with the chorus "When I think about the dirt/ That I'll be wearin' for a shirt/ I hope that I get old before I die." These guys should definitely change their name. It won't be long before they really are giants. (Express Music, 175 Fifth Ave., New York, N.Y. 10010, $8.98)