That's how I've always understood it; otherwise if you're syncing separate bands across 2 different channels then the TAG x1 design wouldn't make any sense. If you use x1 at a single site in a monopolar montage, you train to sync the targeted bands in one location. You can use that in a bipolar montage and I guess you're syncing the averaged activity of each band with the other. But then it stands to reason that x2 in a monopolar montage just does the same thing as x1, plus syncing with another channel--in all, I think that means 4 bands are synced together.
I believe that TAGX2 shows some type of average or compounding of the amplitude across both electrode sites, of any one frequency (ie: theta). I would only add, therefore, to be sure that any design that you are attempting to get to mimic TAGsync isn't merely syncing theta at channel 1 (for instance) with gamma at channel 2 (for instance). I believe that both frequencies have to be measured for through both channels, and the appropriate compounded/average feedback given. In other words, the theta bin is giving feedback for 2 channels and so is the gamma bin. This is my impression. Someone may correct me. This may be how CON2C works, but I'm not sure. If it is, then mimicking TAGsync using it would be trivial. They only lacking feedback would be the high beta (and delta?) inhibits. Though, I don't tend to have much issue staying under those inhibits in TAGsync except when I move around. I'd personally be comfortable doing not overly long sessions without them. I'd also personally be more worried about uptraining delta with theta than I would beta with gamma.
Brain-Trainer keeps updating their website, and they've redone their FAQ section since the last time I was there, and in revisiting the page yesterday I ran across a note by Pete van Deusen on TAG and CON2C that I hadn't seen before that seems relevant to the discussion here. It's just a stub--Pete puts answers to questions in the Yahoo forum in his FAQs often without the context of the specific question, and this note appears to be a response to a question about the TLC7 assessment--but I seem to remember reading somewhere either in the FAQs or in their forum a more extended breakdown on how CON2C is essentially the same thing as TAG Sync. It really seems to me that the bins targeted to suppressing Beta and Delta that Douglas has put in his design are the only significant difference. One of these days I'll have time to muck around in the diagrams in Bioexplorer and compare them, but it'll probably take a full day at least.
TAG Sync (Theta Alpha Gamma Synchrony)
Douglas has certainly made people aware of this protocol, and his version is nicely done from what I’ve heard. Sure alpha, theta and gamma synchrony are desired states, but a bit less than half the assessments I see already synchronize. It would be like training a cheerleader to jump up and down. That’s the problem with buying something you might not need. The assessment will show your synchrony eyes-closed, eyes-open and at task between each site pair in theta, alpha and gamma (and the other frequencies as well). There are alpha synchrony, gamma synchrony, one-band synchrony for delta, theta or alpha, two-band synchrony for alpha and (you choose) theta or gamma. Same as TAG sync in terms of what it does.