I think, Pip, if I understand your needs rightly, that what you really need here is a little rustic symphony-style diatonic hurdy-gurdy which anyone with the most rudimentary wood-working skills could knock out with a bit of time and patience. Something like THIS would do the job just fine. Thing is, over the last 30 years or so hurdy-gurdies have been reinvented as the reserve of virtuosos and master craftspersons, but the basic concept is simplicity itself and I feel a more folksy approach to such things is long overdue...