I actually enjoyed my G70 right off the bat. After all, I was already used to the 'Roland sound' from my G1000, tested and true, and have always eschewed factory presets for my own setups. The V1 G70 came OOTB with a VERY 'European' style mix, quite drenched in reverb, and it seemed obvious that the style voicing had been rushed, to get it out quicker, I guess.
But it took only a short time to fix the reverb and voicing issues, thanks to the easiest style voicing tools in the industry, and I was enjoying it immensely.
V2 brought out the OTS improvements (stored with the Style, now, not in the Registration) and the brand new Guitar Mode (although sadly, only a realtime feature unlike Korg's... mind you, Yamaha have YET to add one of these) plus many other improvements, along with a complete reworking of the Style defaults, to lessen the reverb and address some of the imbalance issues.
Then V3 brought about the per Part and per Drum 3 band Parametric EQ and some other additions, and again, a revoicing to accommodate these new additions.
All in all, I would have had to have bought TWO more Tyros's, to have seen the same degree of OS additions from the original (I don't think Yamaha have EVER added a major feature from newer arrangers to the OS of older ones). That's a bit too expensive for me!
I haven't heard the BK-5 yet, but own a BK-7m. Yes, there are a few improvements (a few new kits have made the already excellent drums even better) and some of the guitars are much improved, and basses over the stock G70 are MUCH better (but mine has the SRX-07 card in, which addresses this), but at the cost of some of the sounds as well. Saxes are a bit less detailed, and some sounds have a smaller choice, but what do you expect from a sub-$1000 unit compared to a $3500 one?
But one thing that Roland HAVE done is spent more time EQ'ing these styles, and I think this accounts for much of what Ian is hearing, over the old G70. But as the EQ capabilities of the G70 are on a par with the BK series, all you have to do is copy some of the default settings from the BK's styles over to the G70, and much of what was missing can be addressed.
Having BOTH G70 and BK-7m, I must admit, I so far have no burning desire to take my BK out on the gigs along with the G70, as close as I can get the G70 to sound, and the way I use them (I'd rather the show was about ME, not how much my gear can do!), and that's not a bad admission for an eight year old piece of kit!
I had a PA3X in my house for a few weeks while I worked on porting Roland styles over for a friend, and I must admit, some of it is VERY nice. But the bottom line for me was, several of the basic areas (particularly the pianos) still took a back seat to my G70, and editing ease was dismal compared to the G70. You COULD do most the G70 can do in this area, but it's MUCH slower and less intuitive. And add to that, the library of US styles for Korg's is still a fraction of what is available for Roland, and once again, it is ALL about the styles in the long run. Plus they have that over-produced edge to them, like Yamaha, that makes it harder to add much of YOU to the mix other than the melody.
Trust me, nothing would make me happier than to dump my behemoth and move to something more modern (and preferably, a bit lighter!) but until someone actually MAKES one (in a 76), I am content. My modus operandi has always been to wait until there is a hugely noticeable difference between what I have and what I want.
Still waiting!
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An arranger is just a tool. What matters is what you build with it..!