Tom Scholz of the band Boston nearly became an inmate of his basement studio in the Boston suburbs, laboring over guitar parts, melodies, harmonies, lyrics and sound mixes. He often worked from dusk until dawn --twisting recording knobs in an obsessive-compulsive dance of which only he knew the choreography.

The days turned to weeks ... the weeks to months ... the months to years and years.

The former MIT engineering student, who admits he's been a "slow-speed thinker" since his college days in the late '60s, ultimately took six years to produce Boston's new "Third Stage" album. He estimates he worked 10,000 hours, punched the recording button nearly a million times and used 100 reels of tape --10 times more than a typical album requires. He even jokes in the album's liner notes that "175 light bulbs burned out in the studio before I did."

"Right now, I have six years of personal life to catch up on. The rust holes in my car are going through the interior; the gutters are falling off my house; and the back rim is falling off my backboard ... . Everything just got spaced during all this," says Scholz, 39.

He was interviewed this week in the Waltham office of his engineering firm, Scholz Research & Development. SR&D makes guitar accessories --used by Eddie Van Halen, Eric Clapton and Jeff Beck, among others --that have gained Scholz almost as much acclaim as his home-basement rock 'n' roll.

Scholz's years of perfectionism have not been in vain. The new Boston album, released two weeks ago, is already in such demand that 2 million copies have been ordered by record stores, while the first single, "Amanda," has been the nation's most-added new song on the radio charts.

"I'm just elated and surprised," says Scholz, whose studio nitpicking also led to 8 million sales of the band's first album in 1976, "Boston," which is still the best-selling debut of all time. That was followed by 4 million sales of the second LP, "Don't Look Back," in 1978.

"I didn't know what was going to happen," Scholz says of his latest release, made with singer Brad Delp and drummer Jim Masdea --the two charter members of the group. "I knew 'Amanda' was going to be a popular song, because I'd heard from enough people who liked it. But I didn't know beyond that.

"I'll be honest with you: It's been as much fun for me with this album coming out as it was for the first Boston album. I didn't know what was going to happen with that one, either. I was surprised if 100 people bought it, let alone millions. And with this one, I again sat on the floor and listened to the radio to see if they were going to play it. And I haven't listened to a radio station since I started the record, except when somebody showed up at the basketball court with a blaster going. Even then, sometimes I'd sneak over and turn it down."

Speaking of basketball, the lanky, 6-foot-5-inch Scholz plays in a couple of suburban leagues as an outlet from music. But last year --when he hoped to finally complete the album --he was fouled during a game, sustaining a back injury so severe he had to finish the album literally on his back. He played the last guitar parts by lying on a surfboard propped up between boxes; and had to call in former Sammy Hagar guitarist Gary Pihl to help out. Even now, during the interview, he's lying on a couch, though he says he's healed enough to try more basketball soon.

The longest recording delays, however, stemmed from the self-critical nature Scholz has had since growing up in Toledo, Ohio, and first coming to Boston to attend MIT. That fussiness intensified when he toiled as a Polaroid engineer by day and a musician by night who gained a recording contract only after years of rejection.

"Why am I so picky? I don't know. I'm not doing this for the money," says Scholz, who still lives in the modest five-room house he had when Boston began. "And it doesn't have anything to do even with the fact that it's a record. I'm sure a psychologist would have an answer right away, but it doesn't matter what it is, or how little a project it is. If it's just writing a short letter to someone, I always end up tearing it up, doing it again and not liking it --spending hours at something that should take 20 minutes."

Boston's new manager, Jeff Dorenfeld, has become so accustomed to Scholz's procrastination that he laughingly threw up his arms when Scholz took a month just to write the album's liner notes.

"Maybe," Dorenfeld kidded him, "you should put something at the end that says: 'I know these aren't as good as I could get them, but to avoid waiting another six years for the liner notes, I'm going to put them out like this.' ''

"I got to admit that speed at picking up things has never been my forte," says Scholz, grinning beneath wire-rim glasses that frame a friendly, high-cheekboned face. "I was like that at school. There were guys who were always out playing sports or drinking beers or whatever; and I was never done. I was still doing a problem set, or trying to finish a project or whatever it was. I was never real fast."

"When I first started on this," he says of the new album, "I would put in, I guess, 50-60 hours a week in the studio. I was there pretty much every day. I really haven't had what you'd call a vacation since I started. But, slowly, I came down, and by the time I finished, after the back injury, I was only working 20 hours a week. By then, I would literally have to drag myself down there. It was like I was two people: One wanted to fool around and go watch the Celtics on TV; and the other would say, 'No, you have work to do.' It was awful. It was very hard driving myself for those last few years.

"And when I was working, I'd work on one song only. I'd try to work on it from beginning to end," he adds. "Normally, I'd work on it a long period of time --I'm talking six months, in some cases. That can get to be pretty trying on your ears, your concentration and everything else. So when you go to bed, all you hear is the song; and you hear it all day long --for months on end. At those times, I would go back and put another song from the album on, just so I would be inundated by something else. Sometimes, early in the morning after I'd been working for a long time, I'd take the time to sit down and listen to another song 20 to 30 minutes to get my mind out of that rut."

Although the album is now signed, sealed and delivered, Scholz still has trouble listening to it for his own entertainment.

"I have to put it on a tape deck and change the speed," he says, laughing. "It's the only way I can listen to it and hear it. I keep telling everybody that after you've heard the same piece of music about 1,000 times, it wears a groove in your brain and you just don't hear the things anymore; you don't perceive them ... It becomes ambient sound. It's like a pilot who doesn't hear his engines any more until one of them starts to skip a little bit. Then he hears it loud and clear."

In terms of sound, the album is similar to the earlier Boston albums with a densely-textured guitar sound covering arpeggiated ballads and powerchord rock, coupled with high-pitched, heartstring vocals by Brad Delp. But the images are more personal, with deeper lyrics about love and maturity. Scholz also reveals in the liner notes that he's become a vegeterian; and includes the addresses of several New Age organizations.

"There's definitely a little bit more of me in this record, and that also made the songs more difficult to write. Realistically, I made a few comments on the first and second records, but they weren't real strong. My primary objective then was just to create some music that was fun to listen to ... . But this time, I definitely decided the whole thing was going to mean something."

As for the title, "Third Stage," he says, "I consider childhood the first stage, adulthood the second, and this is the third stage. Maybe if I live long enough, there will be a fourth stage... But I don't want to say too much about it. I'd rather have people wondering about it's about."

Because the recording went so slowly, Scholz says he needed a diversion. That was why he founded his engineering firm, SR&D, which began in a cramped office above a sub shop and now employs 30 workers in a modern office in Waltham.

"I decided if I was to do anything worthwhile in the studio, I had to do it the way I used to. And I used to do it by having a full-time job. I used to work at Polaroid in their product design group. Actually, I think, I had better song ideas while I was at Polaroid than I did when I was at home around a tape deck. I decided it just wasn't working out, trying to take on writing an album as if it were a job. That's not why I got into music in the first place."

He started SR&D in late 1980, but didn't work really hard at it until 1983, when he was socked with a $20 million lawsuit from CBS Records, which cited breach of contract, claiming Boston owed them five albums in 10 years. The suit will be heard in January --and Scholz doesn't want to talk about it now --but does say the record was held up further because CBS withheld royalties, forcing him to turn to SR&D to make the money to finance his studio tinkering.

SR&D has been successful beyond Scholz's fondest hopes. He first created the Power Soak unit, a volume-control device, and then the Rockman, an inexpensive miniamp, for which 3,000 orders were received before it even left the shop.

"It was just as impossible for me to let go of the Rockman design as it was for this album," he says. "Here we had 3,000 orders and bankers screaming and everything else ... But I didn't like the way the compressor sounded. I knew it could be done right, but it was going to take a little more effort."

The Rockman soon enabled Scholz to communicate with some of the greatest guitarists in the business.

"I'll never forget putting the warranty cards for Jeff Beck's units on the bulletin board," he says. "But I always felt bad that I wasn't the first to put out a record with the Rockman. In fact, I'm probably the last. In the past three to four years, probably every new record has had this on one track. But I was the first one to record with it. It's just that mine took longer to come out."

Now that the album is a reality, Scholz hopes a tour may be planned in the future. He's no longer connected with earlier touring members Barry Goudreau, Fran Sheehan or Sib Hashian, but his group is expected to include the veteran Delp ("he's essential to the Boston sound"), and likely the two other musicians who helped on the album, Masdea and Pihl.

For now, he's just basking in the relief of having the album in the hands of those who offered support during his long years of studio exile.

"In the six years, outside of some people in the business who were looking at this as a profitable thing for themselves, I didn't get any discouraging comments. I might run into people when I stopped at a gas station, and a guy would recognize my rusty car and say, 'Hey, aren't you in Boston?' They'd always say they liked the first two albums and, 'Are you going to make another one?' They never said, 'You jerk, you should have made another one. You got too rich.'

"There were quite a few critical comments made on the air, I understand, but nothing from just average people who listen to the music. So that was a big help. It was those kind of things that keep you going over the long haul."

And what about the fate of his basement studio?

"Maybe I'll turn it into a family room with a Ping-Pong table," he says, laughing. "I think I've worked in that room long enough."