The anglicized spelling of the title of its latest album, "Rumours" (Warner Bros. BSK 3010), is about the only hint we have that Fleetwood Mac's origins are English. Ten years ago, this was a British blues band, and a rather good one. Now, like the pilgrims, Fleetwood Mac has come to the new land, settled comfortably into the new surroundings, even adopted a couple of natives. Their music, as one might expect, has metamophosed too. It has become as much an embodiment of California as the Santa Monica Freeway.

The changes have altered more than the group's sound. Their popularity in the last year and a half has also soared, thanks to their last album (or their "first" if you are inclined to think of this version of Fleetwood Mac as a totally different band from its predecessors), called "Fleetwood Mac," whose success was phenomenal. Released in mid-1975, the record didn't begin to catch on until the end of that year; once it did, sales - which have now reached 4 million copies - kept it in the top 10 for more than a year.

"Fleetwood Mac" was an example of pop packaging at its best. The songs were brief, well-conceived and uniformly infectious; the production was solid, and the performances, especially the singing of Christine McVie and Stevie Nicks, were superb. Gone was the flashy, driving, highly electrified sound of the band's early days, and long gone too were guitarists Peter Greeen and Danny Kirwan, who were responsible - at different times - for most of that sound.

In their place was a leaner, less-demanding sound, highlighted by the vocals of McVie and Nicks, the two women in the band, and the steady rhythms put down by drummer Mick Fleetwood and bassist John McVie, the only original members of the group. Woven through it was Lindsey Buckingham's guitar work, always tastful and economical.

"Rumous" offers us essentially more of the same. Song for song, it isn't as strong as "Fleetwood Mac," but it isn't likely to disappoint anyone who "discovered" the group through that album, earlier.

There are a few changes, but they re subtle ones: Buckingham and Nicks, the two Americans in the band, are asserting themselves more, instrumentally and vocally; there is greater use of vocal harmony by Nicks, Buckingham and Christine McVie, and, in several carefully selected spots, some emotive 12-string guitar playing by Buckingham. The effect is distinctly Californian, very much middle-of-the-road and mid-'60s. Echoes of The Mamas and Papas, the Jefferson Airplane, even the Byrds, can be hear throughout.

The album has a formidable selection of possible hit singles. "Go Your Own Way," the Buckingham composition that was released first (and is the best choice for a single on the record) is already getting as much radio airplay as it can bear, and there are at least three others, Christine McVie's "You Make Loving Fun" and "Don't Stop," and Nicks' "Gold Dust Woman" - her followup to "Rhiannon" on "Fleewood Mac" - that can pick up when "Go Your Own Way" starts to falter.

There is room for criticism here on the grounds that "Rumous" is a "safe" record; the band has found a musical formula, and has opted for staying with it rather than testing itself by stretching out in new directions. Normally I would go along with this, but "Fleetwood Mac" offered a change from the incessant blare of heavy metal and the banal hum of most soft rock that was so refreshing its effects still linger. "Rumours" just gives them a boost.