John Mayer is experiencing a very, very rare crisis of confidence. ''I feel like such a hack. I should just stick to writing pop songs,'' sputters the singer, sprawling across a bench during a time-out from an ''Austin City Limits'' sound check. He's at the TV series' University of Texas set to tape a blues-based show that'll team him up with Chris Layton and Tommy Shannon, better known as Stevie Ray Vaughan's rhythm section, Double Trouble, and guitar great Buddy Guy. Perhaps he'll get in an old-fashioned guitar duel with Guy? ''Yeah, right. Me in a cutting contest with Buddy Guy.'' Damn right, he's got the blues.
But just for a moment, and it passes. It's not as if he's a Johnny-come-lately to tonight's genre. Mayer grew up venerating Vaughan -- ''I'd go through periods of time where I would take all the Stevie Ray posters down and put up Pearl Jam, and then Pearl Jam would come down and Stevie Ray and Buddy Guy would go up'' -- and isn't about to let I'm-not-worthy misgivings spoil one of the greatest moments of his 26-year-old life. This is stuff he dreamed about as a teenager in Fairfield, Conn., training himself to be a master blues fret man, before he went off for a short stint at the Berklee College of Music, where the preponderance of would-be Joe Satrianis turned him off virtuosity for good.
His substitute choice of vocation -- straightforward, (mostly) solo-eschewing singer-songwriter -- has worked out okay. His debut, 2001's acoustic-based ''Room for Squares,'' won a Grammy, went triple platinum, and found him hailed as one of maybe a half dozen ''career artists'' rock has produced in the last decade. An accomplished follow-up, ''Heavier Things,'' just helped him beat the sophomore jinx by debuting at No. 1. It could be subtitled ''Mayer Goes Electric,'' though you'll still have to listen carefully to hear Clapton influences coming through the cracks.
'''Come Back to Bed' is my blues outlet on this record,'' Mayer says. ''But I have this weird aversion to jamming. I like structure.... When people [see me live and] say, 'You wouldn't know you were this much of a guitar player from your record,' I think, 'Right on.' I played maybe 50 percent of what I could play on this record, but it got exactly what it needed. Not every job requires every tool in the box. It's not like I'm fixing a refrigerator and I've just really got to use that socket wrench! It doesn't do a damn thing to the refrigerator, but let me just turn some bolts for a minute.''
As a youngster, Mayer remembers thinking '''I'm going to take blues, and pop songs, and find the middle ground.' I remember Eric Clapton's ''Journeyman'' record as coming close, and wanting to make that happen again.'' He realizes that hybrid remains mostly locked up in his head. ''At the end of the day it's basically pop music,'' Mayer says, ''but I think it's more important sometimes that I'm aiming for that, even if I'm hitting something five feet away and coming up with 'Your Body Is a Wonderland' or 'Why Georgia.''' Even now, on his tour bus, he says he watches a video of Clapton in concert ''before I go on stage, just to remember how to hold a stage.''