MIDI files can be supported, the original example MP3Shield_Library_Demo.ino is constrained to MP3 files. Whereas, FilePlayer.ino example is more flexible allowing various file formats to be played. including MID. The Arduino’s app is arbitrarily filtering on file extension. Where the VS1053, really does not care about, nor even know the file name or its extension.
Note: I think I recall that VS1053 will only play MIDI type “zero” versus “one” and I had to convert my examples to “0”
