Endless soft-rock melody Tuesday. New York’s Infinity Song is an apt name for a soft-rock act with wide horizons. The family band’s mix of expert but casual-sounding R&B and pop recalls ’70s singer-songwriters, injecting some much-needed oxygen into the oft-dour world of indie music. The band is playing Larimer Lounge on Tuesday, July 16, as part of a tour behind new album “Metamorphosis Complete,” released May 30 on Jay-Z’s Roc Nation label.