The spirit of King Crimson is alive and well. The 21st-century schizoid-man sound of local melodic mathematicians Fight Cloud, Mahlion and Houdan the Mystic spread their respective cat’s foot iron claws at Gallery5 on Friday, July 3. Largely defined by their instrumental passages, the three groups share an appreciation of the riff. Fight Cloud embrace Robert Fripp’s steely, six-string precisions filtered through a prism of various classic and alternative rocks, while Houdan the Mystic shares many of the same influences in its measured paces. The group’s carefully considered prog rock is expansively complex yet simple enough not to lose the listener in a deluge of details. Mahlion is post-Bomb Squad hip-hop rock surrealism; Andrew Hoilman’s layered manipulations are cinematic in scope, but rooted in a dance-floor immediacy. The show and First Friday opening takes place 6 p.m.-midnight. Free. gallery5arts.org.