I don't really blame the arranger manufacturers. It's a tiny, tiny niche market, you can't expect them to innovate as fast as the trillion dollar computer industry. That things have even got this far is quite an achievement!
But progress has always crept along. I just think it's our job to push them in the right direction, and that often takes having a good realistic look between what CAN be done, and what can be done AFFORDABLY.
No, I don't honestly expect a VSTi level guitar mode plug-in. But allowing user definable MIDI output for each and every slider, button and knob on an arranger's front panel is the most basic, simplest thing the laziest manufacturer in the world could add!
It's a simple look-up table. No hardware, no new ports, no new buttons, no new styles, no new sounds, no new audio capabilities, no new effects. Just 'When button B is pressed, send xyz MIDI code on this Channel' or 'When slider A is moved, send this sysex'. Then a lookup table for what needs to be sent.
That's eight year old level programming!
I dunno 'bout you, but if I were an arranger manufacturer and half my customers wanted a MUCH better Guitar Mode, and the other half didn't mind hooking up a laptop with one cable, running a VSTi of a top level guitar mode program and all I had to do was make sure my sliders sent any damn MIDI the VSTi wanted to see, I know which would be more cost effective!
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An arranger is just a tool. What matters is what you build with it..!