I've noticed something similar on one of the rock / blues organ tracks - slight distorion occasionally. I'll have to check which one it was and let PG know.
Thought it was my ears / phones as well until I swapped the phones around and the distortion moved to the other ear.
Such may be the result of mic'ing a Leslie cabinet with one mic at the horn level and another down below at the speaker rotor.
It is often the case that these two mics are panned a bit to either side, turning what is originally an "up/down" into a L/R on the soundstage.
When a Hammond Tonewheel Organ is set up for "grit" - typically accomplished by readjustment of the negative feedback capacitor inside the expression capacitor's circuit, and sometimes also with a bit of circuit tweaking of the Hamnmond Preamp as well, the distortion thus created will often first happen at the Horn, which is on a crossover at about 700Hz, leaving the lower bass speaker, typically a 15" woofer pointed downwards into the lower rotor, still sounding rather clean.
When the Blues/Rock Hammond Realtracks were introduced, this old B3 lover, with years at the helm behind him, immediately heard that the organ used for these tracks is of the type that is treasured by players of the roadhouse blues and rock genres, often they prefer a B or C model that has a lot of mileage on the tonewheel rotors, which translates to a different sound than the "tight" B3 sound preferred by most Jazz and players of other genres.
The famous rotary speaker Leslie cabinet also is known for certain sounds "other than the organ" emanating from the cabinet, often only noticeable when the organ is not being played, but not always, such as mechanical noise from the rotation motors, drivewheels, belt pulleys and belt tensioners. Not usually noticed in live performance work, easily spotted when a Leslie is close-mic'd as in the studio.
Matter of fact, many good Tonewheel Organ digital simulators come complete with user-selectable "models" that, while all being B3's, sound very different from each other. The venerable old Native Instruments B4 simulator at one time included an addon pack that allowed the user to choose from "worn" organs and "tweaked" Leslies for just this reason.
In the realworld, no two B3 organs sound exactly alike.
Blues players, Rock players and even some Gospel players often prefer the sound that comes from the older organs in which the capacitor banks were built using the old wax paper caps rather than the poly caps that were built into the organs starting sometime in the mid 60s. Grit, baby. And since each tonewheel has its own separate cap on the circuit, the variance of sound between each note is sometimes all over the place. A rather clean Bb note with a rather raspy D above it, things like that, which actually give the organ that "character".
Don't get hung up in the notion that all tracks MUST be entirely pristine, with the only sound being that of the instrument itself, in the real world, such is the exception and not the rule. Matter of fact, if a Rotary Organ track is "too clean" when solo'd, it is often the telltale sign of a MIDI patch or a poorly designed digital simulation in which the designers did not do what it would take to add the various configurations of distortion, overdrive when Expression pedal is floored but clean when lifted a bit, and perhaps one of the most difficult parameters to simulate authentically, the various mechanical sounds of the spinning rotors. There is also the Wind Noise of the spinning horn in there, too.
Again I attempt to tell folks that the bottom line is how the track sits in the mic, NOT what you hear when Solo'd. Of course, there do exist certain anomalies that may fall outside of these parameters, that would be things like a continuous buzz or hum on the track, which might indicate one of several electronic circuit problems or interferences, there could be certain background noises picked up by the mics - sometimes the performance on the track yields the decision to go with that take anyway, though, as the performance might be deemed to far outweigh the fact that the mics picked up someone coughing, or feet shuffling at one point, or whatever.
Experience with the mixdown of multitracked recordings is likely the missing ingredient with many of these kind of complaints, especially the experience of having to come in after the Tracking phase is completed, on a project you've never heard before and your task is to do the mixdown. First thing I always do in that situation is throw up all the faders, just to see what I've got. From there the task is to make the overall happen from the various tracks and worrying about little anomalies on one track out of a possible 24 won't get the job done - and more importantly, is not likely to be heard or noticed in the context of the full mix.
Signal to Noise is expressed as a Ratio for a reason...
In layman's terms, Signal to Noise means that a low amplitude level sound may stick out when the overall tracks are at a lower amplitude, but that same sound will actually "disappear" when all tracks in use are playing at realworld amplitudes.
Don't get too involved in the "hunt for noises on the RealTracka" unless you find one that actually stands out in the context of a full mix.
--Mac