Tom Scholz had a rather unusual hobby. He'd come home from his research engineering job at Polaroid Corp. in Cambridge, Mass., plug in his electric guitar and record track after track on the tape machine in his basement. Every lick he'd ever loved went onto those tapes, snatches of all Scholz's favorite songs. Local musicians added bass, drums and vocals, and eventually Scholz's tapes found their way to Epic Records. Released in 1976 under the name "Boston," the album Scholz recorded in his basement went on to sell 7 million copies in the United States alone - the largest-selling debut LP in rock history. Boston, who had never played any place larger than a club, was headlining 10,000-seat halls in a matter of months. The first album sold consistently for two years, and Boston's newly released "Don't Look Back" (Epic) promises to do the same.

Guitarist Mick Jones spent some years bouncing around the British rock circuit, playing in doomed late editions of Spooky Tooth and the Leslie West Band and working for a record company, before forming Foreigner with King Crimson veteran Ian McDonald and four unknowns. Jones planned Foreigner's strategy carefully; "success through musical focus" was his motto. Propelled by two driving, inane singles, "Cold As Ice" and "Feels Like The First Time," Foreigner's first album sold more than 3 million copies in the United States. Their second LP, "Double Vision" (Atlantic), is past 2 million already.

That's a lot of discs and tapes. While these sales figures pale compared to a typical prime-time TV audience, they are rare in the record busence, rarer still for debut albums. They indicate that Boston and Foreigner are selling to people who don't normally buy records, people outside rock's usual market of preteen-agers to young adults. Parents are buying these records, too. And that's odd, because Boston and Foreigner play hard rock, with the requisite distorted guitars, screaming vocalists and ponderous beat - generally anathema to older listeners. Yet a huge audience finds these two groups not only palatable, but desirable.

It's impossible to class either Boston or Foreigner as original. Boston's first LP borrowed heavily from such guitar-dominated groups as the James Gang, the Byrds, the Who and the Doobie Brothers, defining each song with a guitar riff. "Don't Look Back" steals more directly - from the first Boston album. (Perhaps the title is addressed to copyright researchers.) Tom Scholz seems content to reuse his old chord progressions and vocal arrangements as long as he can regroup his overdubbed guitars.

Foreigner also sports Who "influences," but their primary source is Free and its more popular heir, Bad Company. In most Foreigner songs, punchy guitar chords alternate with vocal phrases in which Lou Graham tries his best to groan like Free/Bad Company vocalist Paul Rodgers. "Double Vision" breaks away from that formula for an instrumental and two ballads, but the rockers remain thoroughly imitative, and those ballads plunder Procul Harum and the Beaties.

Neither group carries any significant message in their lyrics. Boston, who make the mistake of printing their words, favors self-actualization through rock 'n' roll, partying, greeting the "new dawn" and "takin' it day by day," along with typical lovey-dovey sentiments. Foreigner is slightly more pernicious: They offer gross come-ons ("Hot Blooded," their current hit), angry misogyny ("Back Where You Belong") and utterly insincere lovelorn laments ("I Have Waited So Long"). None of the lyrics on "Double Vision" or "Don't Look Back" would severely tax the intelligence of the average 7-year-old.

Boston and Foreigner's real accomplishment has nothing to do with their songwrithing. What they have done - with considerable success - is to completely remove hard rock's threatening undertones. When the Who or Led Zeppelin unleash a power chord, it echoes with violence - but when Boston or Foreigner do the same thing, the only echo comes fron a reverb unit. Having tamed the style, they can domesticate it as well, turning anarchic hard rock into loud Muzak for millions.

Boston's transformation is the more radical one. Foreigner is easy to take simply because their materials are so familiar, while familiarity is only one factor in Boston's accessibility. It is Tom Scholz's production and arranging that make Boston's accessibility. It is Tom Scholz's production and arranging that make Boston's sound ubiquitous. His style is easily explained: guitars everywhere. Rhythm guitars high and low, two and three parallel lead lines, guitars doubling bass riffs, guitars doubling vocals . . . anyplace a guitars line can go, it goes (although occasionally a keyboard is heard somewhere, for variety). Scholz almost compulsively fills every sonic niche, and he gets a sound that is powerful but cushioned. Part of hard rock's jangling effect comes from the gaps between parts, and Scholz has systematically eliminated those gaps. "Don't Look Back" is music heard through a guitar fanatic's ears; even vocals, usually the center of a pop production, are subordinated to Scholz's six- and 12-string structures. Actually, "Don't Look Back" seems obsessive; Scholz often starts a song with so many parts going that there's no place left to bulid. The drama that made "More Than a Feeling" Boston's first hit single is missing.

At this point, Boston and Foreigner are so well entrenched that they are immune to criticism. They are harbingers of a new hard rock geared to the mass market - derivative, formulaic, determinedly inoffensive and, seemingly, unstoppable.