Up to a point Chuck Yeager ....
what you say is true for piston engined helicopters, in the power on clutch engaged mode.
Turbine powered helos have no solid connection between gas generator (the engine) and the power turbine and rotor. So engine rpm (ggrpm, N1, Ng) has no fixed relationship to rotor rpm or Nr, and will change with power demands....
I guess that's got sciencedoc really confused now...