Los Angeles — What do you do if you've been singing, writing songs, playing saxophone and keyboards in one of the world's most popular rock 'n' roll bands and suddenly the band disbands? If your name is Cornelius Bumpus and the band is the Doobie Brothers, you take a tip from Cole Porter and ''pick yourself up, dust yourself off, and start all over again.''
Not that Cornelius had much of a chance to get dusty. While the Doobies were still performing together, Cornelius came out with his first solo album, ''A Clear View'' (Broadbeach Records). Now, less than a year after the Doobies' final concert, Cornelius has a new album, ''Beacon,'' and a new band, logically called the Cornelius Bumpus Quartet. And now the music is pure jazz.
Four in the morning at a Howard Johnson's restaurant is neither the ideal time nor the ideal place for an interview. But since Cornelius had finished up a two-night engagement in Los Angeles at 2 a.m. and had to be in Santa Cruz the next day - or rather, later that same day, 4 a.m. - HoJo's was it.
''I think I've discovered my real self playing in the quartet,'' Cornelius began. ''I've learned a lot from being in the Doobie Brothers: how to perform in front of large numbers of people, how to make friends, in fact how to communicate better. But in jazz there's greater freedom of improvisation. Jazz is based on improvisation and spontaneity, both of which are also a big part of life, too. There wasn't as much improvisation with the Doobie Brothers. I'm not down on rock 'n' roll. But I think you've got to figure out where you fit and go there.''
In the quartet, Cornelius plays tenor and soprano saxophone and flute. He also sings.
''I played keyboards with the Doobie Brothers, but now it's just a writing utensil for me. There are much better keyboard players out there. But playing saxophone has become an extension of my thoughts.''
Cornelius has remained close to the other members of the Doobie Brothers. He plays on Patrick Simmon's new solo album. Drummer Keith Knudsen was there both nights Cornelius played in Los Angeles. He has also stayed in touch with Michael McDonald. But as for the group getting back together again, Cornelius will only say that ''the Doobies were an interesting mixture of personalities.'' He leaves us to draw our own conclusions.
Cornelius fits jazz, or rather jazz fits him, to a T. There are only so many things a jazz saxophonist can do in a rock context. In a jazz situation, the sky's the limit, something Cornelius proves every time he plays. He is a melodic and disciplined horn player. Not surprisingly, he says the first saxophonist he remembers making an impression on him was Eddie (Lockjaw) Davis, an artist who came out of the big-band tradition.
''I never even heard of Charlie Parker until 1968,'' he says. ''I started playing saxophone in the fifth grade. It was either that or the accordion. I played a lot of rhythm and blues first, before arriving at jazz. My family was very supportive of my playing music when I was growing up. My mom used to sing around the house, and my dad was a fan of big-band music. They got me started.''
Cornelius intends to provide the same support for his own children. ''They'll definitely play some instrument. It's like a language to learn, and it's not that hard to learn either. I'm not going to push them into a career of music either. But they're definitely going to have a lot of music around them while they're growing up.
''My son already has a baby drum set. The first day, he started playing with both hands! I got him a toy clarinet, too.''
Cornelius's son was also the inspiration for a beautiful jazz waltz he composed. But he didn't start writing music until about six years ago. A question about how important writing music is to him causes Cornelius to pause for several moments, seeking solace in his cheeseburger and root-beer float. (There are no rules for eating at 4 a.m.)
Finally he says: ''I started writing love songs at first. I guess I was trying to figure out what love is, and it started coming out in songs. I didn't even have a girlfriend at the time. But I figured the only way I was going to be prepared for being in love was to work it out mentally.''
Now Cornelius writes love songs for his wife, Linda, and their two children, Aaron and Megan. ''I have an image in my thinking, like a symbol of purity,'' Cornelius continues. ''That's what I want to project with my music: a clean sound. I want the audience to understand the lyrics when I sing them, and I want them to have a substantial message. I want to find a way to say 'I love you' and mean it.''
He adds: ''There's a message in the fact that the words and the melody in my music are generally happy - and in the fact that the musicianship is good. There's nothing sloppy. Most lyrics today tell kids all the wrong things. We've got to tell them something different. I want to be able to lift people's thoughts. And I find that a lot easier to do in jazz than in rock.''
Even Cole Porter would probably agree that Cornelius Bumpus isn't really starting all over again - he's rising again. This new step in his career is a graduation, with honors.
''Even if we keep playing only small clubs, we can still make a living at it, '' he says. ''Besides, it's pretty exciting, starting from the ground floor again. The challenges are neat. I can see us building up steadily, and it feels great to be playing. I can't tell you. . . .'' He pauses and grins. ''Yes, I can tell you: It's wonderful.''