In 1998, as an opening night present for his musical, A New Brain, Barbara Finn offered her son the greatest gift she could – her life.

"My mother died a week and a half before the premiere," Bill Finn says on the phone, from his Manhattan apartment. "She called the whole family in to her bedside and told us she had just taken morphine so that everyone would be free to be there on my first night.

"We sat there with her for a while and then ... she was gone."

But not really. Finn immortalized his mother, who was terminally ill when she died, in three of the selections that lie at the heart of Elegies: A Song Cycle, which starts performances Feb. 15 at the Berkeley Street Theatre Upstairs.

"After she died, I couldn't write anything for a while," says Finn, his voice thick with emotion. "Then I slowly began to create a tribute to another friend who was gone – Jack Eric Williams – the original Beadle in Sweeney Todd.

"Somehow, that opened the door and I began writing all sorts of songs about all sorts of people who weren't around anymore."

There's nothing new about Finn's using his life as the raw material for his songs, because he's been dipping into the well of autobiography for nearly 30 years to create some of the quirkiest but most heartfelt musical theatre of our times.

He was born in Boston, Mass., on Feb. 28, 1952 and describes himself as having been "on the fringes all my life, ever since childhood."

When he entered Williams College, it was as an English major who hoped to be a novelist. But Finn soon found himself writing musicals.

And it appears that his unique way of looking at things was there from the very start, with his first show about the execution of Ethel and Julius Rosenberg, called Sizzle!

"Is it any wonder," he laughs, "that I had trouble getting produced?"

But Playwrights Horizons in Manhattan took an interest in him and staged his shows In Trousers and March of the Falsettos. They're the works in which he introduced the world to Marvin, who leaves his wife Trina and son Jason for a sexy young guy named Whizzer.

Of these works, Finn says, "They're not overtly autobiographical, but they're autobiographical in a sense because I am gay, I am Jewish and I use all of my feelings in what I write."

March of the Falsettos' 1981 run was an off-Broadway hit and Finn was the man of the hour for a while. But – by his own admission – "I am the slowest writer in the entire world."

Aside from a 1983 flop called America Kicks Up Its Heels (reworked in 1989 as Romance in Hard Times), he didn't do much for the rest of the decade. But then, as he saw AIDS destroying so many of his friends, he made himself go back and finish off the Marvin musicals with Falsettoland, in which Whizzer succumbs to the disease.

It opened off-Broadway in 1990 and – two years later – joined with March of the Falsettos to form the show known as Falsettos, which won Finn the 1992 Tony Awards for Best Book and Best Music and Lyrics.

Then, during that charmed summer, "just at the moment I should have been happiest," he says "death tried to pay me a visit. I've been fighting him for years. Death is not to be preferred."

Finn's vision and balance started going. He was diagnosed with a massive brain tumour and was told to put all of his affairs in order before undergoing surgery.

But he didn't have a tumour; he had a rare condition called AVM (arteriovenous malformation) which could only be cured through a variety of complicated procedures.

He survived them all, regaining his full functions, but once again it took him a long time to self-start creatively. When he did, it was with his most autobiographical show to date, A New Brain, about a composer diagnosed with a brain tumour.

It was during this period that his beloved mother, Barbara, became terminally ill and brought about her own death so that everyone could attend her son's opening night, which returns us to the 18 songs of Elegies.

"My big fear in tackling this," confides Finn, "is that I wouldn't write a song that would bring my mother back to life."

The ones he composed about her ("Infinite Joy," "When the Earth Stopped Turning," and "14 Dwight Ave., Natick, Massachusetts") pleased him. "I was writing way above myself," he shares, "and sometimes when you're writing really well and you realize it, it can freak you, but this time, it didn't."

So the memories and the songs kept pouring out. Some, like the one to impresario Joe Papp, have a cheeky charm and bravado. Others, like "Mark's All-Male Thanksgiving" (written about gay activist lawyer Mark Thalen) careen giddily from hysteria to heartbreak in the course of one number.

There are tributes to chiropractors, actors, grocers, dogs – anyone whose life touched Finn.

But in the middle of all this personal mourning and healing came an day that went beyond anything Finn had contemplated writing about: Sept. 11, 2001.

"I thought, `How can I disregard this? This is so seminal to everything about grief and mourning in our world.' But yet, it was so different."

And so Finn wrote a climactic sequence about people dying and losing those they loved in the Twin Towers. He himself now feels "it's the musical and emotional climax of the show."

When he was finished with the work, he called up Andre Bishop, artistic director of Lincoln Center Theatre and said "Would you like a show about dead people?"

Finn auditioned it for Bishop who said, "It's the most powerful thing I've ever heard and I don't know what to do with it." He eventually put it on for a series of Sunday and Monday night performances in 2003, resulting in an original cast recording and dozens of performances around the world.

Finn's most recent work is the current Broadway smash, The 25th Annual Putnam County Spelling Bee, which shows a considerably sunnier side of the composer. He believes that creating Elegies made it possible.

"I'm happier knowing that I've written those songs."

And when asked what his mother might feel about the trio of musical numbers he composed to honour her, Finn chooses his words carefully.

"If there's possibly another world, I'd like to think she can hear me say, `Jeez, ma, I hit it out of the park three times for you.'"