Inside the wood-panelled auditorium of one of Tokyo's most prestigious concert halls, 24-year-old Kiwa Usami presses just one index finger to the piano and summons the colossal swells of Beethoven's Ode to Joy, accompanied by an orchestra and choir.

Usami, who has cerebral palsy, was one of three musicians with disabilities performing Symphony No. 9 with the Yokohama Sinfonietta at Suntory Hall on Thursday using an artificial intelligence-powered piano. 

To assist players, the "Anybody's Piano" tracks the notes of the music and augments the performance by adding whatever keys are needed but not pressed. 

Usami, who started playing piano while in elementary school, helped inspire the AI programme. Her dedication to practising with one finger prompted her teachers to work with Japanese music giant Yamaha. 

The result of their collaboration was a revised version of Yamaha's auto-playing piano, which was released in 2015. Thursday's Christmas performance was the first such concert.

"It's a really powerful experience to play with an orchestra," 10-year-old Yurina Furukawa told AFP after a rehearsal on Wednesday.

The "Anybody's Piano" allowed Furukawa, who has a rare muscle condition called congenital myopathy and requires breathing assistance, to perform from a bed stationed in front of the grand piano. 

Keeping rhythm by moving her left arm, she powerfully pressed the keys with the back of her right hand, with the AI-assisted piano filling in the notes to complete the performance.

Unlike more traditional auto-play, the "Anybody's Piano" stops if a player hits the wrong notes.

"When I miss a key or slow down, I feel the pressure from the piano to go on and press the right key," said performer Hiroko Higashino, 39.

Higashino, who was born with three fingers on her right hand, only began learning to play piano after the "Anybody's Symphony No. 9" concert programme was announced.

"If the piano helps me and adds two missing keys for me, I can more faithfully recreate the rich harmony, the music that Beethoven intended to express," she said.

Members of the 130-person audience described the Christmas performance as uplifting.

"I haven't had such a heart-trembling experience like this for a long time," said Teruko Imai, a concertgoer in her 60s.

"It was the best Christmas present for me."

Another attendee, Koki Kato, 16, said she was "so touched".

"The piano makes it possible for anybody to perform, which is a very good thing for music too."