Why is volume proportional to pitch?

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Why is that? It's really extreme. A note sounds so much louder than the one just half an octave below it that it's impossible to write anything with a moderate pitch range. I learned from the lmms wiki how to adjust the "base note", and it seems that the volume is determined by how far above the base note it is. Is there any way I can make the volume constant?
Volume is constant. It's your hearing that isn't.

Read up: http://en.wikipedia.org/wiki/Psychoacoustics
It doesn't matter if it's the human ear or the sound waves. I want to know how to make it sound the same.
Use equalization. C* 10-band is pretty good.
hmmm....strange, I have never had that problem. What plug-in, preset, etc. are you having this trouble with?
Okay, nevermind. It was something in the settings. I toggled a bunch of options that I knew nothing about and it works now.