Dave Segal once wore, “Seattle duo the Grizzled Mighty has one of those self-descriptive names that show a blunt confidence in what they’re doing: robust blues-rock, without an iota of irony. In order not to sound like stodgy revivalists, bands of this ilk need to conceive riffs you want to hear repeatedly and deliver them with a ferocity and inventiveness that suggests the musicians have made a deal with el Diablo.” A portion of donations from tonight’s online performance will benefit the NAACP Legal Defense Fund.