Icelandic post-rock band Sigur Rós may be on an indefinite hiatus, but the group's enigmatic singer Jon Thor Birgisson, better-known as Jónsi, is filling the void with his first solo album, "Go." Having driven Sigur Rós' music in a more poppy direction on recent albums, Jónsi descends into pure pop on his new collection of songs, using instrumentation ranging from harpsichords to flutes. But much of the solo effort retains Sigur Rós' influence. The track "Sinking Friendships," on which Jónsi's calm and collected vocals swell into intricate instrumentation, shares the same low-key vibe of some songs found on the band's 1999 album, "Agaetis Byrjun." And the foreboding string and electric guitar arrangements of "Kolnidur" could've easily fit onto Sigur Rós' 2005 set, "Takk . . ." But "Boy Lilikoi," the first single from "Go," sounds completely different: Jónsi sings with a cheerful energy that matches the flute chirps and cymbal crashes of the song's background.