profezzorn, I've been thinking and playing around a bit with error notifications.
Currently there are 3-4 errors that have talkie voice notifications. While it's cool to have voice messages with a pretty low memory footprint, they don't sound very good (and are often hard to make out) and the message itself is not exactly what the error is (ie Bank Open means a file was not found).
I wondered about putting recorded audio messages in program memory. Paul Stoffgren (Mr. Teensy) has done some work on this. Paul estimated that you could put 20 seconds of audio in program memory of a Teensy 3.2. I made 4 error messages using a test-to-speech website and came up with 4 seconds of total audio, so that would take 1/5 of program memory. Is this a direction you think is worth pursuing? The plus side is the audio error messages would sound better and be exactly what you want, but is it worth 1/5 of the program space? Let me know what you think.
Another option would be to put error audio files on the SD card. Of course this doesn't work for SD card or file errors. Perhaps beeps could be used if the SD card can't be read (ie 1 beep means low battery, 2 beeps means no SD card, 3 beeps means file not found, 4 beeps means bad blade). Or maybe just use beeps and no voice messages. Again, your thoughts?