It depends on [seq] from cyclone, and the [mscale] and [markov] abstraction. And OF, ofxPd, webMidi and Emscripten.
https://forum.pdpatchrepo.info/topic/11722/mscale-transpose-notes-according-to-given-scale-and-root
https://forum.pdpatchrepo.info/topic/12147/midi-into-seq-and-markov-chains

Here is the patch: https://webmidimarkov.handmadeproductions.de/
And here is also a PD only version: https://github.com/Jonathhhan/ofEmscriptenExamples/tree/main/midiFileMarkovPDversion

Here is an improved version (its now with [midi] from else): midifilemarkov.zip

There is a seperate version for Linux and Windows, because [midi] formats the midi files dependent from the platform differently into .txt files.

And here is an example (I know, its a neverending project ):

And here the updated webversion: https://midifilemarkov.handmadeproductions.de/

Now its also possible to write the markov chain into a midi file (and also to download it from the website ):
TeenTown3markovOrderRemix.mid
midifileMarkovRecordWindows.zip

Here is an updated Windows version (with a small change it works with Linux too): midifileMarkovWindows20220220.zip