That brain-freezing falsetto is unmistakable -- it will chill you to the bone and leave you mystified. If you're a fan of Sigur Ros, you already know its power. The owner of this delicate instrument is Jonsi, best known as the lead singer and cello-bow-playing guitarist for the post-rock purveyors. Jonsi helped guide the Icelandic band to international acclaim following the release of their breakthrough second album, 1999's Agaetis byrjun. After 16 years with Sigur Ros, Jonsi finally broke out on his own, releasing his solo debut album, Go, in 2010. He brought in partner Alex Somers (whom he worked with under the moniker Jonsi and Alex for the 2009 album Riceboy Sleeps), producer Peter Katis and classical composer and arranger Nico Muhly to flesh out what was originally planned to be an acoustic album. What resulted is a gorgeous arrangement of strings, brass and woodwinds, highlighted by Jonsi's inimitable, part-English, part-Icelandic croons.