Complex sentence: The song featured backup by Carlisle, Chet Atkins, and Carson's sister, Opal, now known as Jean Chapel; it was, curiously, not a hit in its initial incarnation, but it gained momentum continuously over the next several years.
Split into simpler sentences: The song featured backup by Carlisle, Chet Atkins, and Carson's sister, Opal, now known as Jean Chapel. Although the song was not a hit at first, it gained momentum continuously over the next several years.