My grandfather Jock Hume was a violinist in the Titanic's band, playing until the ship went down. He was 21. At 2.20 am, the last lifeboats long since gone, he joined 1,500 men, women and children in the sea, his violin case strapped to his chest for extra buoyancy. Half an hour later they were all dead from hypothermia. More than a thousand were never seen again.

No one has ever told the story of what happened after the Titanic sank. It is more shocking than any of the events that led to the foundering of the great liner. Jock's pay, along with the rest of the crew, was stopped at 2.20 am. Two weeks later, before his parents had been informed of his death, they received a bill for the brass buttons on his bandsman's tunic. Later still, when it was confirmed that Jock's body was among only 328 recovered from the sea, they were told that "normal cargo rates" would apply if they would like his body to be brought home to Scotland.

One hundred years on, the story of the aftermath has many uncomfortable contemporary parallels. The White Star Line was a fast-growing company that had become self-serving. Having failed in its duty of care to its customers, it accepted no responsibility for the deaths and never said sorry. Sounds familiar? The captain went down with the ship but the chairman escaped with his life - and fortune - intact. A corporate cover-up that could teach today's spin-doctors a thing or two swung into action and a corrosive class system, operating as ruthlessly in death as in life, applied another coat of gloss, making the deaths all so terribly brave.

My book started as a family research project: what had caused Jock, a brilliant young fiddler, to leave home at 14 and travel the world playing in ships' orchestras? The answer was a dysfunctional family with its own modern resonances. In the year before his death I discovered Jock had crossed the Atlantic three times. Then he was given a booking a young musician could only have dreamed of: a chance to play in the orchestra on the world's greatest passenger liner. When he returned from the maiden voyage, he was to marry his fiancé Mary. My mother was born six months after his death and a bitter battle ensued between the two families.

All the bodies recovered from the wreck were taken to Halifax, Nova Scotia, most of them by the cable ship Mackay-Bennett. My grandfather is buried there, alongside 120 other Titanic dead, forty of them still unidentified. In the archives in Halifax I read the log kept by the captain of the Mackay-Bennett, revealing the forensic horror of the sweeping up operation. And even as the bodies of the dead were being unloaded, 54 seamen in Southampton were arrested for mutiny for refusing to sail to New York on the Titanic's sister ship, Olympic, until there were a sufficient number lifeboats. More than 700 families in Southampton had lost a father or son on the Titanic.

For a hundred years, the Titanic has cast a long shadow over successive generations of families who lost loved ones on the ship. Jacob Astor, whose body was recovered close to my grandfather's, also left an unborn child. Both men, in their different ways, exhibited great courage that night, Astor saluting his young bride Madeleine after helping her into a lifeboat and stepping back as the lifeboat was lowered. He then went below decks to the ship's kennels where he released his much loved Airedale terrier, Kitty. But death in the North Atlantic was no leveller. On the Mackay-Bennett, the body of Astor, who was carrying $3,000, was embalmed and placed in a coffin. Jock, who had a violin mute and a few pence in his pocket, was thrown on to crushed ice in the hold until the ship returned to Halifax.

And The Band Played On begins where the other books and films all end: the moment the ship goes down. It's a must for anyone interested in the Titanic - as well as anyone who is considering researching their own family history, for it is above a human story uncovered by dogged detective work revealing some astonishing facts. When you turn over a stone as large as the Titanic, you never know what you will find.