WHO-1. That's the serial number on the first Memorymoog synthesizer to hit the road.

The newly-developed computerized keyboard instrument is making its concert debut with The Who on their North American tour, which steers into a sold-out Rich Stadium Sunday afternoon.

In Moog Music's Cheektowaga factory to pick it up earlier this week was the man who will be playing it, the unheralded fifth member of the Who.

He's Tim Gorman, a native of Oakland who's been a sessionman in England for the past dozen years, working primarily for producer Glyn Johns.

His credits include the short-lived mid-70s pop group Ram, a late '70s band called Lazy Racer, in which The Who's Kenney Jones drummed briefly, and the sessions which produced the Rolling Stones' "Emotional Rescue" and "Tattoo You" albums.

Johns called Gorman in for The Who's latest effort, "It's Hard."

He's continuing with them on the road and expects to be part of their future studio projects.

"Mainly," he says, "my job is to fill things in and hold the production together. They've been using a lot of keyboards and sequencers for quite a while now. It's a very integral part of their sound."

There's a world of difference between working with The Who and working with the Stones, Gorman says.

The Stones let their sessionmen improvise anything that comes to mind, while The Who have quite specific ideas of what they want.

As for the open antagonism between singer Roger Daltrey and guitarist Pete Townshend, Gorman explains that they cultivate it.

"Their policy is to keep the knife's edge sharp," he says.

"It creates a sort of honest hysteria and I think that's what the fans come to see.

They respect that honesty."