I'm reading Thomas Pynchon's Vineland, and I came across a phrase I'm unfamiliar with. For context, Zoyd (the main character) has taken a job playing music on a temperamental synthesizer in a flying Hawaiian-themed cocktail lounge.
Zoyd was presented with a thick tattered fake book full of Hawaiian tunes, and on the lounge synthesizer, a Japanese make he'd heard of but never played, he found a ukulele option that would provide up to three orchestral sections of eight ukes each. It would take several flights across the Pacific Ocean and back before Zoyd felt easy with this by no means user-friendly instrument. The critter liked to drift off pitch on him, or worse, into that shrillness that sours the stomach, curtails seduction, poisons the careful ambiance. Nothing he could find in the dash-one under the seat ever corrected what he more and more took to be conscious decisions by the machine.
What the heck is a "dash-one" in this context? Googling the phrase (or searching on this site) yields a lot of people debating whether to use one dash or two when writing, so it's difficult to find this phrase in any other context.