By Michael Levitt , Elle Mannion , Scott Detrow Singer and musician Willow released her seventh full-length album Petal Rock Black as complete surprise, continuing defy expectations with her music. SCOTT DETROW, HOST: OK, it is Friday. It is time again to kick back and listen to some new tunes. This week, we are listening to something completely unexpected. (SOUNDBITE OF SONG, "SITTING SILENTLY") WILLOW: (Singing) Sitting, sitting silently, sitting silently, sitting, sitting silently, sitting... DETROW: "Petal Rock Black" is the seventh full-length album from Willow, who released the record last Tuesday with little warning. For this week's New Music Friday segment, we are joined by Evan Miller from WYSO in Yellow Springs, Ohio. He's here to tell us about the new album. Hey there. EVAN MILLER, BYLINE: Hi, Scott. DETROW: So this kind of, I mean, happens a lot more than it used to, but this came out of nowhere (laughter). What do you make of Willow's decision to release this as a total surprise?…