At first glance, there’s nothing so complicated about what the Thermals do. They find a good riff, lock in on it with drums, guitar, and bass, and go right at it. On the other hand, there is sophistication there in the group’s sense of melody and probing lyrics. The Radio Room’s outside tent wasn’t even full when the Thermals started their set, possibly because: 1) The Thermals had played SXSW several times already; 2) This was one of the only showcases at the Radio Room without free food; 3) After two days of nonstop music, 1:15 in the afternoon starts to feel like the crack of dawn. Whatever the case, it didn’t bother the Thermals, who tore through a set of songs from their strong recent records. Bassist Kathy Foster pogoed and bounced around, and there was a good amount of energy for so “early” in the day.