At the Frasier retirement center in Boulder, the voices of the Tremble Clefs reverberate inside a sunny room. Most of the singers are living with Parkinson’s, a neurological disorder that can cause tremors and difficulty walking or talking. They are strengthening their voices and exercising their many muscles by singing together.

They’re also having a really good time for a Wednesday morning at 11 a.m. Two seniors are holding hands, and another is dancing with her walker. One singer, Bill West, has driven 45 minutes from his home in Lakewood to be part of the fun. It’s joyful. And some singers say it improves their symptoms and mood.

Among the singers is Davis Phinney, the former professional and Olympic cyclist who was diagnosed with Parkinson’s at age 40. Phinney, now 60 years old, is a legend for both his cycling prowess in the 1980s and 90s and his advocacy for Parkinson’s. This morning, he has just finished a spinning class around the corner before singing with the Tremble Clefs. He has direct eyes, a wide smile, and the trim physique of someone who has spent a lifetime in Boulder.

“My voice has had a slow degradation. There’s a soft, slurry aspect,” he says. Phinney notes that singing has given him confidence to sing a cappella to warm up his voice before speaking to sometimes hundreds of people at events for the Davis Phinney Foundation.

Phinney works on pushing his voice forward and out of his throat while singing, which he says helps him speak more clearly and more quickly in general. Phinney attributes that tactic to the Tremble Clefs’ music director Rachel Newson.

Newson (a stunning mezzo-soprano) directs both the singers and accompanying pianist and guitarist during rehearsals. “Throw a frisbee full of air with your voice and see if it will help you,” she tells the singers. “It’s better to sing loud and wrong…Smack me with your sound.”

Music and rhythm have been shown to improve gross motor skills like walking and balance for people with Parkinson’s. Now, new research in Denver is exploring how they might improve fine motor skills like buttoning clothes or using a pen to write.

Isabelle Buard, assistant research professor at the University of Colorado Denver, is studying the effect of music on the brains of people living with Parkinson’s. She’s looking at a part of the brain called the basal ganglia. Faulty connections in the basal ganglia make movements difficult for people with Parkinson’s, and  she hopes to bypass those “broken” connections by strengthening other pathways in the brain when combining rhythm and music (her study does not involve singers in the Tremble Clefs).

“We’re using music, instruments, and specific techniques to help restore those brain pathways,” Buard says.

How can Buard see those pathways? In her study, she uses a brain scan called magnetoencephalography (MEG) to measure brain activity in people with Parkinson’s as they lie on a bed and tap their fingers to rhythms. Then, participants take 15 sessions of guided neurologic music therapy, and they practice fine motor skills by playing the keyboard and castanets. After five weeks, they return to Buard’s lab for another brain scan to measure whether their brain activity has changed (she’s still collecting data for the study).

“Music has such a powerful effect on the body and brain that we need to understand it better,” she says.

The Tremble Clefs’ guitarist, Bill Wood, says he didn’t think he’d play again after his Parkinson’s diagnosis five years ago. But medications helped relieve his tremors and he recently switched to a smaller guitar to make playing easier. Wood, 81, is no stranger to music, once recording with Joan Baez before a long career as a molecular biologist at the University of Colorado Boulder.

We have a good time, says Wood of playing guitar and singing with the Tremble Clefs: “It just feels good.”

Paul Zeiger, 83, wears a plaid shirt and has soft hazel eyes behind his small glasses. He grew up singing in a Lutheran church and playing the trombone in bands. “I’ve always loved music and now it has a specific effect to ameliorate the symptoms of Parkinson’s,” he says. Zeiger was an electrical engineer and chairman of the computer science department at the University of Colorado Boulder.

“Singing brings me in an upward direction,” says Zeiger of his rehearsals with the Tremble Clefs. “These folks sing as well as any group, but they have more skin in the game.”

If You Go: The public is welcome at the Tremble Clefs’ free concert at 2 p.m. on Saturday, December 14 at Frasier in Boulder.