This reminds me of an 'incident' with our old Keyboards Player, Hugh McKenna from the Sensational Alex Harvey Band. Hugh was not very technically literate (but a brilliant pianist). The battery that supported the motherboard of his Korg gave out and we promised to replace it for him before a gig. We had done our research and printed out various instructions on how to do the 'op'. Said battery was buried about 3 mother boards down, so we had his keyboard spread over quite a lot of the stage before successfully replacing the battery. Huw was quite nervous but we exuded an air of confidence. When we put it back together and it went through its set up was the point that I discovered that Keyboards could be tuned to different pitches (I didn't know this at the time). We opted for one only to discover that it didn't conform with all our instrument tuning. We ended up tuning by ear as the audience were wondering what's going on by then. At the very last minute I found the menu option for correct tuning (causing us to have a second panic), but at least Hugh was happy!