On gently rolling terrain I will sometimes just shift between the big and small chainrings, depending of course whether I'm going up or down, and leave the rear alone. This doesn't always result in the ideal gear/cadence, but there are times when I don't care much about that.
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1989 Schwinn Paramount OS
1980 Mclean/Silk Hope Sport Touring
1983 Bianchi pista
1976 Fuji Feather track
1979 raleigh track
"I've consulted my sources and I'm pretty sure your derailleur does not exist"