Hi Musikman,
If you just want to use the MoES at a rather superficial level then it's not too hard to use. If all you want to do is to pick a voice (program in Korg speak) and play it or to pick a voice and apply an arp to it and then play with that, then it is relatively easy to get around the keyboard and get those things done. HOWEVER, if you want to get inside and do some fairly complicated or sophisticated things then hang on to your ass because the OS is convoluted and TOTALLY nonintuitive and you will spend a lot of time at Motifator.com trying to get answers about how to do something, and you may or may not get any answers. One thing is for sure (I've seen it happen) though, and that is if you suggest that maybe perhaps there could possibly be something WRONG with the way the OS is laid out and that MAYBE it could be better done, the Yamaha reps may very well flame you and then ignore you.
I had a MoES for about two weeks and then took it back and got a Tyros (which I love!) because I'm retired and do music for personal enjoyment and I just simply did not feel like fighting with that damn OS! On the other hand, the Tyros, even with it's short comings, which ALL keyboards have, is totally different. It is well laid out and is intuitive to use and easy to get around on. I'm very glad I took the MoES back and got the Tyros.
These are just my personal feelings and your mileage may vary.
Tom
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Bigger is not always better
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Bigger is not always better