I agree that a real drummer has a vast range of timber and nuance at his fingertips... But a real guitarist, a real pianist, a real violinist and a real just about ANYTHING has the exact same degree of nuance.
Yet we use sampled recreations of THOSE sounds quite happily. And they keep getting better and better all the time, as keyboards have ever larger and larger ROM sizes, for more and more samples. To be quite honest, I think, if you listen to some of the better drum VSTi's out there, you will find yourself VERY hard pressed to tell that they aren't live drumming. Sure, one or two samples for a ride cymbal simply is not enough to fool anyone. But 24-48 or so? Pretty hard to tell that from the real thing. You even have 'round robin' triggering on some of the better VSTi's, so if you send it an old MIDI file or style where every single note of a drum sound is at the same velocity, the VSTi will alternate between several different (but similarly recorded) samples, so you don't get the machine gun effect.
So, if you put the sample count up high enough, basically the only way a listener can tell if it is a machine is if the programming of the groove is appalling. Which, if they are triggered by real drummers on a MIDI drum kit, should not be the case.
So, once again, I disagree that audio drum loops is the BEST way to get better drum grooves in arrangers. If arrangers start to have MUCH larger sample counts for the drum kits (which some of them already are, albeit in a bit limited fashion so far) and the grooves are played by real drummers on TOTL MIDI drum kits, you get SO close to the sound of the audio loop, it is pretty much indistinguishable from the real thing.
BUT...
The advantage of doing this rather than loops is obvious. For starters, every single style you have can use these improved KITS. Not just the paltry few that come with your arranger that have audio loops. And while you can take the audio drums of one style, and copy them over to another style, you can't do a damn thing about the mix, the sound, the groove, the kit, the ambience. They are all written in stone.
But a VSTi quality MIDI drum kit can do the exact same thing we already can do... Maybe you want the style the way it is, but with brushes instead of sticks? Maybe you want a piccolo snare instead of that fatty maple? Maybe you'd like to have the style swing a bit, rather than be four square? Maybe you'd like the toms a bit wetter?
Can't do ANY of that to an audio loop.
It all boils down to prioritization... The arranger manufacturers have spent a FORTUNE trying to get more and more realism and accuracy out of the sounds we PLAY... amazing sax sounds, guitar sounds, B3 sounds, grand piano and Rhodes's. But sadly, the drum section hasn't QUITE got the same love. But rather than suck it up, and add a bunch of ROM to significantly increase the drum sound range (the more samples, the more dynamics and nuance), Ketron first, and now Yamaha are diving into the audio loop solution. I think it's a mistake.
You want realism in arranger drums? You can have it without painting yourselves into a corner with loops. You can have it without ANY of the shortcomings of audio loops. But you have GOT to do it with better kits.
Loops are a dead end. The future is sampled kits. They just have to get bigger in size, just as out sampled pianos had to, or our sampled saxes had to, or our guitar sounds had to.
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An arranger is just a tool. What matters is what you build with it..!