Gathering dust in an attic, a long-forgotten recording has lain buried for more than 40 years, never played in public.
Aashish Khan's untitled 1969 collaboration with George Harrison is thought to be the inspiration for the Beatle's song My Sweet Lord, released the same year. The earlier song is six minutes long but its significance is far greater than the sum of its parts: a medley of Khan's haunting ragas on the sarod interspersed with Harrison's rock guitar.
Its notes hark back to both a contemporary western fascination with Indian classical music and a burgeoning of fusion music, of which 72-year-old Aashish - the last in a long line of famous Indian musicians - was a pioneer.
"At that time, people did not know the word 'fusion'," he says during a flying visit to Dubai, where his sister Lajo Gupta has lived for 25 years.
"George and I became friends while working on a movie production. The filmmakers wanted a song based on pop music so I asked for his help because I did not know what pop music was. He played the intro and a solo in the middle on guitar while I sang. It was based on the fact we are all children of God.
"The movie was never [properly] released and neither was the song. Maybe I will release it one day. It is a gorgeous track and it will be huge when I do."
The Khan family boasts a musical heritage stretching back to the court of the 16th-century Mughal emperor Akbar the Great.
As the eldest of 12 children, it was expected that Aashish would continue the family tradition, as his father, Ali Akbar, had done before him. Aashish's grandfather, Allauddin Khan, who played more than 200 instruments and is widely credited for reinventing the 18th-century Maihar gharana school of Indian classical music, taught him to play the sarod from the age of five.
A cousin of the Arabian oud, the 25-stringed lute-like instrument has a deeper, more resonant sound than its close relative, the sitar - an instrument popularised by Ravi Shankar, Aashish's uncle.
"By the age of eight or nine, I was practising 12 hours a day and being home tutored," Aashish recalls. "My grandfather learnt in a very hard way and wanted to pass on what he knew to his disciples. It used to annoy me sometimes that I did not have any free time to do anything else.
"He was very strict and when he beat me, I used to hate it. I never had the normal life of a child."
Aashish's experiences echo those of his father. Allauddin was a perfectionist. Accordingly, his son's lessons started before dawn and often lasted for up to 18 hours.
Ali Akbar once wrote: "If you practise for 10 years, you may begin to please yourself; after 20 years you may become a performer and please the audience; after 30 years you may please even your guru. But you must practise for many more years before you finally become a true artist - then you may please even God."
The violinist Yehudi Menuhin, who invited Ali Akbar to America in 1955 as curiosity about Indian classical music was beginning to grow, called him "an absolute genius, the greatest musician in the world".
Aashish's father went on to establish the Ali Akbar College of Music in California and taught when he was not on tour. He also played alongside Eric Clapton, Bob Dylan and Harrison at the Concert for Bangladesh in New York in 1971, although he claimed that the music was so bad he had to stuff toilet paper in his ears.
Aashish had much to live up to. When he was 12, he first performed on stage with his virtuoso relatives at the Indira cinema hall in Calcutta.
"It was the first time we had all played together," he says. "Part of the stage broke because so many people stood on it. It was very exciting. I still have that feeling when I am playing a big concert but after 10 minutes, I just forget the audience is there."
He left India to help set up his father's school, then performed his first overseas concert in the Purcell Room of London's Southbank Centre in December 1967, later going on to tour throughout Europe. He also formed one of the first fusion groups, Shanti, with the tabla player Zakir Hussain in 1969, playing the sarod using a Fender guitar amplifier with a vibrato effect.
In addition to collaborating with Harrison on the soundtrack to his now-cult film Wonderwall, he discovered a love of jazz and partnered the likes of Alice Coltrane, John Handy, Charles Lloyd and the pianist John Barham. At the same time, he began teaching at the University of Washington in Seattle.
Sadly, Shanti disbanded in 1972 and Aashish's performing career has suffered from bad management and a number of other setbacks since.
"That was the biggest blow," he says of these tough times. "I was going through a lot of hardship. I had just got divorced and it was difficult for me to survive."
Still, he continued to play concerts in India and still performs regularly to this day in the jazz-fusion bands Shringar and Inner Voyage.
Now, it appears that Aashish's own musical lineage has come to an end. He has remained estranged from his only son, Faraz, since an acrimonious divorce more than 20 years ago.
However, Aashish still hopes to pass on his skills to a younger generation of musicians. Four years ago, he took up a teaching post as a professor of Indian classical music at the California Institute of the Arts in Los Angeles.
"Last year they made me a permanent member of staff," he says with pride. "Whatever I know, I try to teach my students. I want them to at least appreciate the music.
"As I grow older, I am finding how difficult that is. It is not just playing mechanical notes - you have to teach the soul of the listener. Only in the last four years have I been at peace. My whole life has been a struggle… but that is the life of a musician."