In the catalog of Swedish music, there are long lists of pop stars, metal bands, producers, DJs, and singer-songwriters. (Oh, and we can’t forget Eagle Eye Cherry.) With a few exceptions, psychedelic rock bands are not a common Swedish export. At least they weren’t, until Tussilago began releasing music last year. The Stockholm four-piece have slowly and steadily gained a following, and with their latest single, that’s likely to grow even bigger. “Say Hello” progresses slowly through blissful, building moments, all while staying true to the great prog rock and psych rock bands of yesteryear. One listen is like hopping in a time machine back to 1970, where you can practically see the people twirling with flower crowns in their hair, one hand around a lover, the other holding a joint.