Karen, Richard and other musicians, including Gary Sims and John Bettis, also performed as an ensemble known as Spectrum.
Spectrum focused on a harmonious and vocal sound, and recorded many demo tapes in the garage studio of friend and bassist Joe Osborn.
Many of those tapes were rejected by record companies.
She and her brother, Richard Carpenter, formed the 1970s duo Carpenters.
Although her skills as a drummer earned admiration from drumming luminaries and peers, she is best known for her vocal performances. Karen Anne Carpenter was born in New Haven, Connecticut, the daughter of Agnes Reuwer (née Tatum) (March 5, 1915 – November 10, 1996) and Harold Bertram Carpenter (November 8, 1908 – October 15, 1988).
The family moved in June 1963 to the Los Angeles suburb of Downey.
When Carpenter entered Downey High School, she joined the school band.
Bruce Gifford, the conductor (who had previously taught her older brother) gave her the glockenspiel, an instrument she disliked and after admiring the performance of her friend, Frankie Chavez (who idolized famous jazz drummer Buddy Rich), she asked if she could play the drums instead.
She and her brother made their first recordings in 19. Under a doctor's guidance, she went on the Stillman Diet.
She rigorously ate lean foods, drank eight glasses of water a day, and avoided fatty foods.
She was 5' 4" (163 cm) in height and before dieting weighed 145 pounds (66 kg; 10 st 5 lb) and afterwards weighed 120 pounds (54 kg; 8 st 8 lb) until 1973, when the Carpenters' career reached its peak.
By September 1975, her weight was 91 pounds (41 kg; 6 st 7 lb).
From 1965 to 1968 Karen, her brother Richard, and his college friend Wes Jacobs, a bassist and tuba player, formed The Richard Carpenter Trio.
The band played jazz at numerous nightclubs and also appeared on the TV talent show Your All-American College Show.