When Hanson scored a 1997 hit with its indelible single “MMMBop,” it was easy to mistake the trio of young Oklahomans for yet another contrived boy band, albeit one that could actually play its instruments and which favored a bouncy bubblegum take on ’60s rock, pop and soul to lip-synced modern R&B.

At that point, guitarist Isaac, keyboardist Taylor and drummer Zac had already written 100 songs and been recording on their own since 1992. Now, after two albums for Island, the brothers are once again on their own. They became some of the rare independent artists to land in the Billboard Top 40 — their third studio release, “Underneath,” debuted at No. 25 — and they’re striving with some success to position themselves as a credible indie power-pop band, as well as “musicians for life,” as Taylor says.