I heard these guys (er, girls) play a little while back and they were incredible, to say the least! If the Punch Brothers had an upbeat rock sister-band, Alto would be it. They just released their debut track, "Vocable", to stream and download for free. Beautiful vocals, a catchy melody, and just a dash of bluegrass make this a track you will have on repeat for a while. They've been working in the studio recently, so be on the lookout for more new material in the future.
