By Geoff Edgers
Globe Staff / February 20, 2011

In his basement, the gawky engineer fresh out of MIT painstakingly recorded layers of guitars, keyboards, and bass until he got it right. But it wasn’t until Tom Scholz, the stubborn perfectionist, met Brad Delp, the dark, complicated singer with the soaring voice, that those basement demos came alive.

They became Boston, a band that dominated the FM airwaves through the 1970s with hits such as “More Than A Feeling’’ and “Don’t Look Back.’’ Boston’s 1976 debut remains, at 17 million copies, the second biggest-selling in US rock history. It launched Scholz, Delp, and the band’s three other members into a world of sold-out arenas from California to Copenhagen.

The sensation of their rise was matched by the bitterness of the breakup of the original five members, who last performed together in 1979. Scholz and the three other musicians, later cast from the band, have battled in the press, courts, and Internet ever since. And no part of the feud has been as ugly as the latest: the fight over who or what caused Brad Delp, the man in the middle, to take his life in 2007.

Now a pair of defamation lawsuits, filed by Scholz in the wake of Delp’s suicide, have exposed new details about the bitter turmoil within the band that preceded Delp’s death. And they have led to revelations about the never-before-reported relationship problems that burdened Delp in the last year of his life.

Scholz’s legal team is contending that Delp’s problems with his fiancee led to his demise, while his opponents point to the decades of dissension within the Boston family tree — a fracturing that deeply troubled Delp. A Globe examination of hundreds of pages of depositions, affidavits, e-mails, and other court filings linked to the lawsuits — one against Delp’s ex-wife, Micki, the other against the Boston Herald — provides a fascinating backstage view of a band that has sold more than 30 million albums over the years.

The band’s history is particularly tangled because of marriages by members, with the dueling alliances they created, and because Scholz and Delp remained the only clear constants in an ever-changing group lineup. Even after Delp’s death, Boston continues on with Scholz, other musicians, and new singers.

The cases have put attention back on the 1970s version of Boston, while also thrusting a group of lesser-known figures into the band’s saga, including Delp’s fiancee Pamela Sullivan and Richard Kilbashian, a sometime soundman for Delp’s Beatles tribute band, Beatlejuice. Their stories, along with those presented by others in testimony, provide a portrait of a deeply depressed man who, because of his own aversion to conflict, kept his true feelings from many who considered themselves closest to him.