The Isley Brothers, 'The Heat is On' (1975)
Journeyman R&B outfit the Isley Brothers are one of those weird bands with a career so long and varied that they don't seem to belong to any one era. Casual music fans have likely heard the group's 1959 hit single, "Shout," or maybe 1966's "This Old Heart of Mine (Is Weak for You)," released on the Motown label. Starting in the late nineties, lead singer Ronald Isley became a go-to hook man, lending his gritty vocals to tracks by the likes of Nas, Wu-Tang Clan and R. Kelly. That longevity means that some glorious music is bound to fall through the cultural cracks. Take, for example, 1975's No. 1 stunner The Heat is On, a simmering stunner divided into a funky A-side and slower, sensual B-side.