Mmmmm lots to digest there ... as posted my velocity was static ( preset) . did not do transpose as MiDi sound was enhancing the organ sounds the sound box (XG100) fed back into the organ amps ..
@wkrug,granddad: Thanks for the compliment. I'm a New Yorker. We're always pushed into getting everything done "yesterday".Wow - Your development speed is abnormal!
For "normal" usage of this display You need 7 lines to the Controller, but You can switch it to serial mode via solder point.
But I think You've known this.
And I guess it's quite expensive.
Don't forget the power supply, the contrast pot and backlight for the display in your schematic - I've done this a time ago.
Such displays are availible es OLED version too, that will increase the viewing angle.
20x2 chars. SPI ? - I've not explored.
My favorite would be a grafic display, You know.
But with an 4 Wire SPI Bus You can change it when want any time.
You only have to use an other library.
You can put an DSO at the 2 sample lines ( or a logic analyzer ), when pressing a key.Typically, the keybed scan rate is around 2000Hz. That seems to be what everybody else is doing. (Roland, et.al.)