[/quote]
For very important weddings, I take this controller keyboard as a back-up keyboard, together with one of my small modules:

http://www.roland.com/products/a-500s/

It fits into the trunk and stays there during the gig, I bought a used one for just 85 euros. Even works on batteries.

(EDIT: Warning: This one is discontinued, but the newer A-49 only works with a computer attached - VERY stupid.)[/quote]

When I got a Roland A-49 a few years back, I, too, thought it was stupid the A-49 could not power up as a standalone. I found a trick on the internet.

How do I power up my Roland A49 MIDI controller with a USB power supply (without a computer)?
Article #1725357 Added on Jun 8, 2015 at 2:16 PM
Hold the Function, Assign, and Pitch buttons while plugging the unit in to the power supply to enable the controller to receive power in standalone. Once you�ve done this, each subsequent boot should work normally with the power adapter without having to press that combination of buttons.