Many have forgotten, or perhaps were never aware, just how much jazz comes out of Kansas City and the American Southwest.

Maybe you think of Waylon Jennings and Willie Nelson as Texas' gift to music. Well, how about Jack Teagarden, Hot Lips Page, Illinois Jacquet and Harry James? You think Merle Haggard was proud to be an Okle from Muskogee? Then so, too, were Barney Kessel, Don Byas and Joe Thomas. And Kansas City? Kansas City! Just imagine that one overgrown cowtown gave the world Count Basie, Lester Young, Mary Lou Williams, Charlie Parker and Ben Webster, to mention - as they say - just a few.

Now, admittedly, not all of them were born there (Basie came from as far away as Red Bank, N.J.), but they all matured there musically. They flocked to Kansas City because it was a kind of regional mecca for jazz musicians - or, perhaps better put, a launching pad that sent one after the other of them scaring off into the big time.

The latest reminder of Kansas City's important place in the history of jazz comes to us in the form of an album by pianist and bandleader Jay McSham, "The Last of the Blue Devils" (Atlantic SD 8800), one that bounces with the good-time spirit of the place and moans with the same lonesome bluesy sound that can be heard to this day down at that famous corner of 18th and Vine. It provides convincing evidence that McShann was at his prime and is still today a first-rate jazz soloist.

On jazz piano, he strikes a rough bargain between the rhythmic, understated style of Count Basie and the more florid invention of Art Tatum (who, during the last years of his life, was a great friend of McShann's) - kind of an Oscar Peterson-cum-barrel-house.

Yet no matter how accomplished he is a soloist, Jay McShann will always be best remembered as a bandleader - and for very good reason. His was the last of the big bands to come out of Kansas City - Count Basie's and Andy Kirk and his Clouds of Joy preceded him - and make it in the great world beyond. What did the Jay McShann band have going for it? A nasal-voiced singer with a distincitive blues style named Walter Brown; a hit record, titled "Confessin' the Blues," that sold a half-million copies in 1941; and a 21-year-old kid in the saxaphone section named Charlie Parker.

That's right, Bird first recorded with the McShann band. He also traveled with it to New York City, in January 1942, for the band's first New York engagement at Harlem's Savoy Ballroom opposite the well-known Lucky Millinder Orchestra. They're still talking about the way the original bebopper marched out onto the stage during "Clap Hands Here Comes Charlie" and proceeded to take the band through some 30 up-tempo solo choruses and blew the Millinder bunch right out of the Savoy. Charlie Parker liked New York, and New York liked him. he decided to stay there.

The Jay McShann band broke up during the war, a victim of wartime travel difficulties and of the American Federation of Musicians recording ban. McShann made an effort to start up again with a big band after the war - but the era had passed, and he was one of the few years on the West Coast with a combo - then finally headed back home to Kansas City where he has kept right on playing all these years.

It was in Kansas City that Atlantic Records found him and then brought him to New York to record this new album, his first in a couple of decades. He was provided with excellent sidemen for the date, including a front line - trumpeter Joe Newman and tenors Paul Quinichette and Buddy Tate - right out of the Basie band. It is a remarkable occasion, a kind of musical reunion of old friends. The atmoshpere is so relaxed, the blowing so easy and congenial, that if it weren't for the absence of the sound of clinking glasses and general hubbub from the crowd, you would swear that what you were hearing was a real, old-fashioned Kansas City bar jam.

On the album are a couple of Jay McShann's hits from his big-band days of the '40s - "Confessin' the Blues" and "Hootie Blues" - on which McShann sings the vocal originally done by Walter Brown. His style is hip, laid-back and satirical where Brown's was a bit more earnest.

The same might be said of his style on piano. He gives the impression that he is in very close touch with music today, for in a few little touches - quotations and musical put-ons - be lets you know he's been listening to them all but has decided to keep right on going his own way.

And that way is, for the most part, good old-fashioned straight-ahead blowing. He and the hornmen do beautifully on "Jumpin' at the Woodside" and a Paul Quinichette original, "Blue Devil Jump"

One last point. The title of the album, "The Last of the Blue Devils," is something of a misnomer. Jay McShann was never a member of that distinguished early Kansas City band, the Blue Devils. It was chosen, however, because McShann is so prominently featured in a soon-to-be-completed documentary movie on Kansas City jazz of that same title. "The Last of the Blue Devils" should be released sometime early next year.