Are you able to hear the difference due to the modification? This was recorded directly out from the Mono/Poly into my M-Audio recording device. VCO1 only, sawtooth waveform, filter wide open, no resonance. To my ears, both the stock and the modified versions have lots of good "buzz", but the modified version has (to me) a little extra brain-tingling sizzle to it. Hopefully, the YouTube audio compression still allows that extra little tingly sizzle to come through. (Note: when I play this video on YouTube, a weird hashy noise comes in around 0:45...that's YouTube, not my synth.)
Now, we should talk about the effect of subtle changes in sound. In the demo above, maybe you'll hear the increased sizzle and buzz. Or maybe you won't. Or, maybe you'll say that the original version sounds better because it sounds more balanced, whereas the modified version has too much sizzle. That's a fine opinion. An important part of this equation is what sound reproduction equipment I use. Recording straight from the keyboard into the computer (or M-Audio recorder, in this case) is not how I normally play, so the recordings in the video above are not representative of my everyday experience of how I hear my keyboard.
When I play, I play live through a keyboard amplifier with a big speaker (Roland KC-550). Sure, there are higher-fidelity sound systems out there, but I just like that live feel where the bass from a big speaker really rumbles your guts. The KC-550 has that. Unfortunately, through this keyboard amp, the sizzle that you hear in video for the stock Mono/Poly is often not apparent...the sizzle gets lost in the amp, or in the room, or in the off-axis orientation of my head relative to the amp. With this modification, though, the extra sizzle makes it to my ears...and it makes me smile. So, for me, the subtle 3-6 dB of added high frequencies makes a small but pleasurable difference.
Maybe six months from now, though, I'll be complaining about how I hate the sound. I'll say that the extra high-treble is too fatiguing. That would be so me. I am a human being after all. Very fickle. :)
Thanks for checking it out!