The cause of death was renal (kidney) failure, publicist Harlan Boll said.
' Love Will Keep Us Together, ' the title track from the duo's 1975 debut album, reached No. 1 in the US in July of 1975 and won the top Record of the Year prize at the following year's Grammy Awards.
He also included a quote from Tennille: "He was a brilliant musician with many friends who loved him greatly. I was at my most creative in my life when I was with him", Tennille said in a statement.
Daryl and Toni tied the knot in November in 1975 but Toni filed for divorce in 2014, after 39 years of marriage.
"I loved him with all my heart", said the 75-year-old Tennille.
"Captain" Daryl Dragon and his wife Toni Tennille of the Captain and Tennille, pose at a convention on July 27, 2005, in Las Vegas.
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A Los Angeles native, Dragon was the son of Oscar-winning composer Carmen Dragon and singer Eloise Dragon and was himself a classically trained musician.
Beginning in the late '60s, Dragon was the keyboard player for The Beach Boys. Mike Love nicknamed him Captain and Dragon began to wear his trademark Captains hat.
Tennille said in a 2010 blog post that Dragon was suffering from an unspecified neurological condition that gave him hand tremors, seriously affecting his ability to play keyboards.
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Before Dragon's foray into traveling with the Beach Boys and then Tennille, he started a musical career with the Wright Sounds. They married in 1975, a year after they signed a deal with A&M Records.
Tennille's spokesperson said "they remained in constant contact and were dear friends to the end". Dragon died early Wednesday.
Dragon is survived by his brother, Doug Dragon, and two nieces, Kelly Arbout and Renee Henn of California.