Dear Tonnie.

I don't think the prob's Sforzando - I've just hit this for the first time. I think the problem's how they tune the darned soundfonts in the first place!

OK, admission time, I'm not the world's greatest computer guy so I'm talking from personal experience, not Deep Knowledge here. As soundfonts all come from different sources, I think their definition of 'equal temperament' differs just a little. Just enough to mix a little salt with the sugar. What's needed is SOMETHING in Sforzando to let you change the tuning up or down in microtone steps until you've matched all the soundfonts up on one chord. Once you've got them all singing from the same hymnsheet, they're fine!

At least that worked for me - I deconstructed some using Audacity (played them in my DAW, output the sound as a .WAV, imported the .WAV into Audacity, microtuned them and exported the result as a .wav, dropped it onto Sforzando and got a new soundfont.) Once they were all tuned TOGETHER, they sounded fine
It's the tiny bits of sourness adding up that's the problem, I feel.

Yours respectfully

Chris.