Endsongs marked Longwave's proper debut in fall 2000. It was an impressive first record, full of lush string arrangements and heavy guitars that helped differentiate the band from such New York City contemporaries as the Strokes. Two years later, Longwave displayed a darker disposition on the Day Sleeper EP. Within a week of its release, the Strokes' manager asked Longwave to play three dates with his stylish five-piece, and Longwave's solid performance quickly landed them a permanent opening spot for the rest of the tour. Such an opportunity boosted the band's profile and led to a contract with RCA Records. By the year's end, producer Dave Fridmann (the Flaming Lips, Mercury Rev, Mogwai) had relocated the musicians to his Tarbox Road Studio in Upstate New York to work on Longwave's major-label debut.

What followed was the dreamy williwaw of The Strangest Things, released in March 2003. Another EP, Life of the Party, followed one year later, but founding members Marchese and James left the band soon after its release. Drummer Nic Brown and bassist Christian Bongers stepped in as temporary replacements, allowing the band to resume recording its sophomore album with producer John Leckie. There's a Fire was released in June 2005, but the subsequent merging of Sony (RCA's parent company) with BMG resulted in Longwave's exit from the label. Disheartened, the bandmates took a brief hiatus, with Schiltz touring the country as Albert Hammond, Jr.'s guitarist in the interim. The boys got back together in 2007, and a series of spirited writing sessions helped reestablish whatever momentum had been lost. Longwave signed to Original Signal Recordings in mid-2008 and released Secrets Are Sinister that November, having recorded the album in Brooklyn and Bridgeport, CT.