After a lot of reasoning and googling I found an easier & faster way to use karaoke files in a DAW
Just download LoopMIDI, then create an evocative virtual MIDI port: mine is KARport
Now, open Ableton Live and set the Input of any plugin to KARport as showed below
Then, open a KAR/MIDI player, or better a scoring tool as suggested by @jjfagot
I tried first to retrieve my paid version of Notation Composer, but my license was expired, so I downloaded their free player Notation player 4 due to its interface that has both fonts and GUI scalable, and I can say it works very well, with the further advantage to see chords and notes
At the end send its output to KARport and match the relevant instrument to each MIDI track: job done
I think I’ll use this system to practice the technique with my various keyboards, and I’ll certainly use just simple MIDIs, i.e. those that contains 4-5 max instruments
After some test I realized that drums are always on channel 10, Bass is often on channel 4, and the other instruments are variable
Anyway, making it simple and using just small “bands” finding the matching is easy
General MIDI was part of the original MIDI spec for just such things as this. Designed with certain things on specific channels. Drums on 10 was part of the spec to keep this unified.
Unfortunately, just drums are on channel 10
The bass is often on 4 but not always, and the others are extremely variable
BTW I found a drawback with certain plugins, where starting a new song in the MIDI player resets their pattern to the default
This is not a problem for AAS Strum because the default is still a guitar, but it’s disastrous e.g. for AAS Amalog Orchestra where the default is an odd percussion
The General MIDI spec was designed to keep this logical and compatible in the early days. At one time QuickTime would play MIDI with built in sounds using this spec. But as you can see not everyone utilized the spec as it was designed. I doubt anyone uses General MIDI when designing things these days.