Norman Martin, 93, and Islwyn Morgan, 89, joined Treorchy Male Voice Choir in 1947 - and are still going strong.
The pair, who are both vice presidents of the choir, have attended more than 6,500 rehearsals and notched up over 2,000 concerts.
Choir chairman David Bebb said their achievement was "staggering".
"Surely, they must be the longest serving male voice choir members in the world today," he said.
"Their contribution to the choir knows no bounds and we look to them frequently for advice and support when decision-making takes place."
One of 10 children, Mr Morgan was the son of a well-known Treorchy choir conductor, and followed his brothers into the choir when it reformed after World War Two in 1947.
"The Treorchy Male Choir has played such a massive part in my life that I cannot imagine being without it,"  said the former officer for the old Rhondda District Council.
The chorister, who performs in the ranks of the first tenors, added:  "I've made lifelong friends, met some wonderful people and travelled the world - things I would never have done had I not been part of the choir."
Choir colleague Mr Martin also joined up in the same year, after hearing the sound of singing as he walked past a rehearsal at a local school.
He spent 25 years working in the coal industry after becoming a collier at the Park Colliery when he left school at age 14.
Determined to better himself, he studied at night school to gain engineering qualifications, and was eventually appointed as a lecturer at Rhondda College, where he spent the next 27 years until his retirement.
Along with Mr Morgan, the two have performed alongside the likes of Ella Fitzgerald, Shirley Bassey, Tom Jones, Burt Bacharach, Katherine Jenkins and Julie Andrews, as well as guest appearances on the Royal Variety Show and for the Prince of Monaco.
"To think that one moment you're being introduced to the Queen and the next you're singing in the Sydney Opera House or visiting the White House. It is absolutely unbelievable," added second tenor Mr Martin.
A retired lecturer and a valley's civil servant are celebrating 2017 as some of the world's longest serving choir members.