(CNN) -- The Sound of Philadelphia is without the sweet soul notes of Bernie Wilson, following the death of the Harold Melvin and the Blue Notes baritone on Sunday.
Wilson died of undisclosed medical complications at a hospital in Voorhees, New Jersey, according to Philadelphia International Records.
Wilson was a member of what's called the "classic" Blue Notes line-up that included Teddy Pendergrass, and that signed with Philadelphia International in 1972, beginning a four-year string of rhythm-and-blues classics that defined the Philadelphia sound.
Harold Melvin, Lawrence Brown and Lloyd Parks rounded out the quintet's line-up at the time.
The group made its 1972 chart debut with "I Miss You" and followed with its first No. 1 rhythm-and-blues hit -- and first Grammy Award nomination -- "If You Don't Know Me By Now." Other Harold Melvin and the Blue Notes hits from that time include "The Love I Lost," "Wake Up Everybody," "Bad Luck" and "Don't Leave Me This Way."
Harold Melvin and the Blue Notes were one of the most popular rhythm-and-blues groups of the 1970s, as their songs ranged from soft and sultry ballads with sweeping and lush instrumental back-up to funk-influenced, proto-disco dance extravaganzas. Their songs were covered by a number of performers as well -- from Simply Red's recording of "If You Don't Know Me By Now" to Thelma Houston's pure disco hit with "Don't Leave Me This Way."
The group never quite recovered from Pendergrass' departure for a solo career in 1976, framed by Parks' departure in 1974 and Wilson's in 1977. Although Melvin toured and recorded with several versions of the Blue Notes into the 1990s, the group never matched its mid-70s success.
Wilson performed with Parks, Brown and John Atkins as The Blue Notes after leaving Harold Melvin and Blue Notes. Parks and Wilson, with Gil Saunders -- also a former Harold Melvin and the Blue Notes member -- toured as a trio for a time in the 1990s.
Melvin died in 1997. Pendergrass, paralyzed in a 1982 car accident, died in January 2010. Brown died in 2008. With Wilson's death, Parks is the only living Blue Note from the Philadelphia International era.