Checkers,
In my helicopter, if I set my power (rotor thrust) to maintain S&L at a speed say halfway between Vmp and Vmo then I can happily climb and descend at constant power simply by changing my speed. This is a critical teaching point for instrument flying (visual flight involves much more TLAR or WMIW).
I know that you use the same technique in descending your aeroplane (say 250kt @ idle isn't good enough - solution: increase to 290kt) and that you may have used it during fuel critical drift up.
Sorry, just being picky....