They even had an audience -- 15 other trekkers paid $10 each to watch the musicians perform for 40 minutes at the summit of 6,654-meter (21,825-foot) high Mera Peak, which is close to Mount Everest and Mount Lhotse.
"My fingers were freezing. It was difficult to play the guitar after a few minutes, but I kept playing," group leader Oz Bayldon said in the capital, Katmandu, on Thursday. "I felt like a 90-year-old with asthma."
Only eight of the 10 volunteers from various countries reached the top, while the two with altitude sickness did not. Local porters helped carry their three guitars, small amplifier fitted with speakers, microphones and a stand. The musicians took turns performing May 16.
"The view was beautiful in the backdrop of some of the tallest and most beautiful mountains. It was like some one had painted it and put it there," Bayldon said.
He sang and played three of the English songs he wrote and one Nepali "mero naam, tero naam," which just means your name, my name.
Frenchman J.B. Tilon, 25, said he was very tired on the way up and did not feel too well. But once he got to the top and saw the view he was full of energy.
"It was the most beautiful landscape I have even seen. It was being above the clouds," he said, adding it was very cold and dry so he was able to play only for five minutes and only one French song.
Bayldon, an Australian living in London, said the group raised 35,000 pounds ($54,300) for a charity in Nepal that is building an orphanage. Other performers are from England, Scotland, Poland and Denmark.
Bayldon set a previous record for highest musical performance in 2005, performing near the base camp of Everest. But that record was broken two years later.
Guinness World Records credits Musikkapelle Roggenzell, 10 musicians from Germany and Bolivia, who scaled Mount Acotango in Bolivia to perform at 6,069 meters (19,911 feet).
Guiness is awaiting the evidence before verifying if the new performance set a new record.