San Diego’s Iron Butterfly undoubtedly are best known for the 1968 proto-metal hit “In-A-Gadda-Da-Vida,” with its hard organ and spooky, psychedelic vocals. Apparently, the oh-so-mystic title actually was inspired by former lead singer Doug Ingle trying to say “In the Garden of Eden” while drunk, so there’s some rock & roll myths dispelled. Like much of the Butterfly’s work, the song isn’t fast or crunchy; rather, the heaviness comes from an acid-drenched sense of looming darkness. The influence on contemporary bands such as Monster Magnet is there for all to hear. Drummer Ron Bushy is the only original member in the band nowadays — no other member predates the mid-’90s. But by all accounts, Bushy has assembled a group of musicians that does the material proud.