Great Pyro. It would be simple to write. Here's how it works. You could have a maximum of 5 (whatever # you want) wav files for each aircraft. Call them eng1, eng2, eng3, etc... The code would call upon each wav file as it enters a percentage maximum manifold pressure. For instance, from 10% - 20% of maximum manifold pressure it would call on eng1.wav, then as it enters 21% of maximum MP, it would begin to call in eng2.wav by slowly increasing the volume of eng2 and DECREASING the volume of eng1.wav. By 25% maximum MP, eng1 would be at zero volume and eng2 woul be at 100% or roundabouts.
The problem with this is that you would need new wav files for each plane. Although that is not a problem for me, it may be a problem for the team sicne you have so many other things to do.
fscott