Looking back, it's obvious that the Miles Davis group was the most influential jazz ensemble of the '60s. From it came not only the first startling experimentations with what is now called "jazz-rock" or "fusion" music, but also some of this decade's most prominent players. For a young musican to be asked to join the master trumpeter's group, said one critic recently, "meant you had arrived."

Herbie Hancock, Tony Williams, Wayne Shorter and Ron Carter, members of the Miles Davis Quintet for much of the mid '60s, have long since "arrived." All four have been leading their own groups for quiet some time now, and Hancock's various funk bands and Shorter's Weather Report have even "crossed over" to the pop audience, achieving the kind of mass acceptance that enables them to play in the same places - and to many of the same people - that rock groups do.

But at last year's Newport Jazz Festival these four highly successful band leaders put their own groups aside for a bit and got together in a "Tribute to Miles Davies." It went well - so well, in fact, that an albun of that concert has been released and the four men, joined by trumpeter Freddie Hubbard, have gone on tour together. They will be at the Merriweather Post Pavilion on Tuesday, and later this summer will perform in Japan and Europe.

"I knew it would work," said Hancock over the phone last week, just after returning from dinner at Miles Davis' home. "These guys are fantastic musicans, and we've always been compatibel. Freddie Hubbard even played on my first solo album, and that was back in 1962. All of us were open to doing a special project like this, because it's a chance to get a perspective on our own progress as musicans and persons. It's great to be together again."

Actually, only the first two sides of "V.S.O.P." (Columbia PG 34683) feature the entire rhythem section of the old Miles Davis Quintet. The other half of the record belongs to pianist Hancock - play ing first with the sextet he led immediately after leaving the Davis group and then with his current funk-oriented band. But, says Hancock, now 37, "the one person whom I cosider to be the link between each of the three bands, the one common denominator, is Miles Davis."

Davis, of course, was the major stylistic influence on Hancock and saxophonist Shorter around the time they were writing pieces such as "Madien Voyage" and "Nefertiti," both of which have been stunningly revived and redone on "V.S.O.P." The music they were playing together at that time, says Hancock, was "really ahead jazz - walking bass, a swinging drum beat," further characterized by "lots of fast eighth notes and long running flowing lines."

It seems strange at first to think of Hancock and Shorter playing in that sytle once again, for their recent work has had an altogether different character. With Weather Report, the 43-year old Shorter has learned to use electricity, play sparingly and make silence count; with his funk groups, Hancock has concentrated more on rhythm and texture than melody lines.

But it's obvious from Hancock's piano solo on "Maiden Voyage" and Shorter's boppish tenor and soprano saxophone forays on "Eye of the Hurricane" that both men were easily able to make the transition back to more traditional sounds. For drummer Williams, who joined Davis in 1963 at age 17, and bassist Carter, 40, it was probably less of a problem to return to their roots: Both of them have been quite active in recent years as session musicians playing a variety of jazz styles.

"Three or four years ago it would have beena lot more difficult for me to go back to playing the kind of music we did with Miles," says Hancock. "At that tiem I wasn't firmly planted enough in what I was doing on my own to be able to look back. But I've learned a lot about the use of space by playing jazz-funk, I think that what I've gained has even filtered over into what we're playing on this tour."

In the year's since leaving Davis, Hancock has become known as a connoisseur of keyboard insturments. On the riff7-based "Hang Up Your Hang Ups" and "Spider," in fact, he is listed as playing 10 of them, including the revoluntionary new Yamaha Electric Grand Piano. "That's only a prototype you hear," says Hancock. "At the time we recorded the album, there were only three Yamaha Electric Grands around, and I had been given on of them."

As played by Hancock during the solo piano improvisation that begins "V.S.O.P.," the Yamaha Electric Grand is a fascinating instrument, with more of an acoustic sound than the Fender-Rhodes that has been the dominant keyboard instrument in jazz and rock the half-dozen years. It has the volume of an electric piano and the clarify of sound of an acoustic grand, a combination that is sure to make it popular in years to come.

Herbie Hancock will surely have much to do with that, for his role these days seems to be the great popularizer of jazz. "There is a new jazz audience out there," he says, "and they like their music funky. The kind of jazz we're going to be playing for them is a kind of jazz they have heard about, but never experienced. I'm hoping that those who know me only for funk will be able to enjoy hard-core jazz too."