I don't really bother with it all that much these days...However, this is something I have used for many years as FOH engineer...Anyway, in terms of the HD Pod I have a couple of suggestions...My own opinion is that the players should not worry about this too much...A good engineer will guide you on this and compensate this accordingly...It is much easier to make this adjustment globally...But every situation is different and human hearing response as it relates to loudness is very key to understanding tone I think...a very healthy endeavor I think...and it is kinda fun to see how much these guys figured out back in 1933...

One would be to use the mid focus EQ...Basically, loudness compensation can be done with a single filter that is about 4-5 octaves wide centered around 1K...The interesting thing that we can do with the HD parm assignments is tie the cut/boost gain and output parameters of the EQ to an expression pedal...I have tinkered with this a little and you can approximate the output level compensation for cut/boost...basically, the idea is to try and keep the output voltage the same...It's not really possible to tie this to the master volume setting...Ideally, the cut/boost would depend on the master vol setting...but then there is the actual sound pressure also which is what this is really all about...Anyway, turning an expression pedal into a loudness morph is a very interesting idea...then again a global EQ in the FX loop can be a fairly simple approach to take...

It's been a few years since I read the paper, but the curves are in there and really as long as you get close it works...Basically it's the same thing a the loudness switch on a stereo...human hearing becomes fairly flat at higher sound pressures, more acute to a center frequncy of 1K at lower levels...That's basically it...FM effect always makes me chuckle a little bit...These were the first guys to map human hearing response scientifically for the analog telephone system...I see it as a response, not an effect...but that's just semantics...

Anyway, I think this is a great read for anyone that is truely interested in learning what the "effect" is and how to compensate for it...For me, being aware of it as long as I have I actually tweak for it all the time...most folks do...when you know that when you turn up the mids might start knocking your head off...The relationship of distortion to sound pressure is an interesting one also...much more complicated and that's kinda where separate tones come into play I think...

how about putting a pod HD Parametric EQ at the end of the signal chain and boosting the highs and lows by about 4 to 6db while you make your patches. Then simply turn off the P EQ when you plug into the FOH. In theory this should correct for the exaggerated Lows and Highs that most players use too much off at low volume.

My advice is to dial in your patches as loud as possible in a good pair of headphones and monitors/PA.  It will sound fine at lower volumes as well, even if it doesn't sound like someone's a$$ is being kicked.  Trying to accurately recreate a FM curve is a challenge.  Even if you did so, you still wouldn't be able to dial in tones at low volume that are magically perfect at high volume.  But the reverse is not true - a tone dialed in at higher volume generally sounds good at lower volumes.