From surf rock in the '60s to the Steve Vai/Joe Satriani/Randy Coven school of shredding in the '80s, a variety of rock eras have had their instrumentalists.

But in the post-Nevermind, post-'80s world of alternative rock, instrumentalists have been harder to find.

Exactly where is the alterna-rock or alterna-metal equivalent of Vai, Satriani, or Coven? Well, such players do exist, but you have to know where to find them.

One of them is Bay Area guitarist Doug Doppler, whose group Doppler, Inc. functions as an instrumental equivalent of Slipknot, Korn, Godsmack, or White Zombie on Nu Instrumental.

This fresh-sounding effort successfully bridges the gap between a Vai/Satriani/Coven/Mads Eriksen type of aesthetic and the world of alterna-rock and alterna-metal/nu-metal.

Doppler is, pure and simple, a shredder; he has the hell-bent-for-chops outlook that Vai and Satriani were known for in the '80s, but instead of trying to sound exactly like his heroes, he updates the shredder tradition.

Doppler provides instrumental rock for post-'80s headbangers who have spent a lot of time listening to bands like Mushroomhead, Type O Negative, and Sevendust and are open to hearing what they might have sounded like as full-time instrumentalists.

Of course, albums as chops-obsessed as Nu Instrumental are an acquired taste; back in the '80s, the people who were more likely to understand where Vai and Satriani were coming from tended to be professional musicians rather than laymen -- they had an appreciation of music that went beyond the superficial, and that is the sort of listener this 54-minute CD will likely appeal to.

You don't have to be a professional musician to enjoy Doppler's considerable virtuosity, but it doesn't hurt.

Regardless of who does or doesn't comprehend this 2005 release, Doppler is doing his part to fill a void -- and anyone who is looking for alt-metal's answer to Vai, Satriani, Coven, or Eriksen is advised to give Nu Instrumental a close listen.