I'm tired so this will be short
Dame Dulce (don't worry, their songs are all in English) are on KNW-YR-OWN records. They are technically a husband/wife duo, but at What-The-Heck Fest (see earlier posts for more info on that) 2003, they performed with four others backing them up. They were supporting their first album, The Sun Comes Into the Kitchen (which is fantastic), but this song was not on it and probably has never appeared anywhere but my computer.
Oh and as far as what they sound like, Andrew's off-key, cracking vocals are either a love or hate thing, while their guitar-driven sound has some minor similarity to pre-2004 Modest Mouse.
Dame Dulce - Cold Canadian Air (live)
EDIT: Thanks to Alex for commenting! Apparently this song has been re-recorded, though this version is still Otherwise Unavailable (tm). Check Dame Dulce's Myspace