My accordion crimes begin almost immediately after I’m commissioned to learn to play the instrument. Owen Murray, the accordion professor at the Royal Academy of Music, agrees to teach me. “Shall I go for the Edith Piaf or the Argentine bordello look?” I ask. “Or maybe Lederhosen?” “It’s been my life’s work to get people to take this instrument seriously,” he says.

He’s right. It is time to take the accordion seriously. Professor Murray has been teaching it at the Royal Academy for 20 years, and in that time has seen this former ugly duckling become something of a swan. His students now win keyboard and woodwind competitions, more and more people play it, and contemporary composers such as Oliver Knussen and Sally Beamish write for it.

Why am I learning it now? Simple. Next weekend there’s a festival in London of the music of the renowned Russian composer Sofia Gubaidulina. And the highlight is the British premiere of her 2003 accordion concerto Under the Sign of Scorpio, written for the great Russian virtuoso Friedrich Lips.

My first stop is to find an instrument. I phone Accordions of London and ask the owner, John Leslie, if I can hire one of his instruments. I soon rule out buying one (a good starter model is at least £1,500), but renting a decent accordion is an affordable £9.50 a day. “Can you play the piano?” he asks. “Yes, I’m quite good,” I reply. “Oh dear,” he says.

Pianists are the bane of Leslie’s life, apparently. We try to make the instrument play louder by hitting the keys harder (quite useless), instead of squeezing the bellows faster (quite proper). However, later, in his shop in Kilburn I get my first taste of the passion aroused by the instrument. “It provides portable harmony! What else does that?” he enthuses. “The guitar?” I suggest. “Pah!” he explodes.

He explains how the accordion works. The sound comes from hundreds of separate metal strips, known as reeds, which vibrate when air is pushed around them. You push the necessary air with a central pair of bellows. When you press a key or button, it sends the air to the reed and you make a sound.

That’s the theory, but standing in Leslie’s fabulous accorducopia, I learn that the instrument comes in all shapes and sizes. On the left hand side a single button may either sound just one note or a whole chord. These systems are known respectively as free bass and standard bass, and some accordions can convert between the two. The right hand side can have piano keys or buttons.

Being a pianist, I decide to try a standard bass piano accordion. Despite Leslie’s warnings, I imagine that my familiarity with the keyboard will help. At first, so it proves. After I get home, it takes only a short while for me to improvise a tune with my right hand, put some jolly oom-pah underneath it with my left. Hey presto: a simple three-chord waltz in C major! “Oh dear,” says Professor Murray, when I tell him what I’ve done. “Why did you get a standard bass? I’d better get a friend to send you a free bass instrument.” He tells me that for the first 130 years of its life, the standard bass system condemned the accordion to a life of three-chord waltzes in C major and prevented it being taken seriously. Oops. Free bass it is, then.

I duly receive the new instrument. It’s a shiny black monster with a terrifying confusion of stops, buttons, switches, dials and converters. I’m not even sure it’ll fit into our two-seater car.

Professor Murray is an inspirational teacher, and we have a fantastic time. First he tells me that the key to everything is in the bellows technique. He takes me through some simple exercises, and I make my first remarkable discovery. The bellows act rather like a bow on a stringed instrument (I also play the double bass). You can attack a note either sharply or smoothly, let it swell seductively in the middle, and fade it out with a soft sigh or a abrupt jerk. In other words, I’m playing like a pianist but I’m phrasing like a string player. What a combination! Then comes my downfall. The left hand doesn’t just push in and out to control the bellows. At the same time it must travel up and down to play notes, and the fingering of the free bass system is phenomenally tricky. Then I have to think about my right hand as well. It’s like rubbing your stomach and patting your head, while standing upside down doing the splits.

When Professor Murray plays for me, I begin to understand what all the fuss is about. The expressive potential of the free bass accordion is phenomenal. Not only do you have access to both chord clusters and melodies in the left hand, you have the huge dynamic range offered by the bellows too. It’s very exciting.

“Rostropovich says that to understand the full possibility of the cello, it’s much better to play with an accordion, not a piano,” the professor tells me proudly. “The accordion can sustain; the piano can’t.” He also describes some of the brilliant effects that Gubaidulina has created for the instrument. He points to a little button which allows air to whoosh out of the bellows so that they can be closed. “When Gubaidulina shows Christ dying in her piece Seven Last Words, she uses this whoosh of sound. It’s the most fantastic musical image.” Murray will perform the work on January 15.

According to Lips himself, there’s never been a better time to take up the squeeze box. “The golden age of the violin was the Baroque era. For the piano it was the Romantic era. The accordion is still changing all the time, and we are just entering its golden era. It’s the most exciting time possible to be playing it.”

I’m inclined to agree. This accordion criminal has reformed.

A Journey of the Soul — The music of Sofia Gubaidulina runs from Fri to Sun at the Barbican, EC2 (020-7638 8891). The premiere of Under the Sign of Scorpio is on Jan 14

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