After many, many attempts to have green keys (those for in-tune solos) working, notably with a Hammond, and after many, many crashes I gave up
I am almost persuaded the culprit is Scaler, because I have crashes with modelled VSTs that doesn’t waste CPU/RAM, and I don’t have crashes even with sampled VSTs and no Scaler involved, so I hope the issue will be fixed in the future, but currently isn’t
In any case, in Italy we say: “Non tutto il male viene per nuocere”
(back translation: not all the bad comes to be harmful 
)
This is why I’m happy that this bug forced me to search for an alternative workflow that involves Scaler doing just chords, and my bare hand (With A Little Help From My Friend Ableton) doing the solo
BTW, I wasted many days to try to understand how having 2 smaller MIDI keyboards joined to have a larger keyboard, because I always believed that each of the 2 Hammond keyboards started where the other ended, but yesterday I think to have understood that they are actually 2 distinct keyboards (with their own generators) that can be used for the same stuff, or for totally different stuff if needed
And in case I understood it wrong, no problem: the motto above applies again
This finding opened a welcome simplification of my Hammond workflow that I explain here
The routings
Scaler delivers chords and the Latch option is selected, so that I can click 1 key on the smaller keyboard, then I can use both my hands on the larger one
The scaler xml
Scaler-State_2021-05-12_023946.xml (6.8 KB)
Thinking to my previous reasoning I decided to skip the drums, because the Hammond used for chords is rhythmic enough alone
Moreover, even if the Bossanova series is 7 chords, I used 2 only: 1st mostly, and the 4th to do a sort-of-chorus
The Ableton trick to do solos without Scaler is… Scale
Nevertheless, just using the same scale used by Scaler, a G major doesn’t work because many notes are out of tune: dunno why
So I had to add another scale before (not after) the root one, and I eventually ended with most notes in tune
The HUGE difference between this trick and Scaler green-keys, is that Scaler lets me play very few (max 5) and similar notes, while Ableton scales let me play the solo over the WHOLE 49 keys keyboard!
The resulting tune reminds me of the sound in Tunng - Comments Of The Inner Chorus, but I’ll upload the MP3 later this night