I liked the way the TRANS (transpose) key works on the "Essential 49/61" . If you wanted to switch to a different key to support a singer or guitar player, say G-Major, just hold TRANS and tap G. Now, with the Essential MK3 I would have to tap 5 or 6 times (semi-tones) while listening to make sure I'm in the right key. This was not an improvement IMO.
The big update features are the new screen with context buttons. Also, the ARP, SCALE, and HOLD modes will definitely get some use. I'm wondering if there is a way to use the MIDI Control Center to reassign keys on the "Essential 49/61" to support the ARP and SCALE functions? They may just be dedicated functions unfortunately.
On the back of the keyboard they've dropped the old USB A (printer) plug in favour of USB C. This is smart because they also got rid of the nearly useless external power plug which I could never figure out why it was there. The Essential 49/61 ran fine on USB power from my computer or USB hub.
They have supported scripts to integrate with "the major DAWs" yet they didn't put one out exclusively for REAPER, which has over a million users by estimates. Arturia published scripts for the Essential 49/61 shortly after release so I imagine those will appear at some point.
