I've heard a lot of ML experiments in making music and I haven't not enjoyed any of them, until this one. Most sound repetitive, bland, unemotional, cold, unoriginal, tedious.

This one is different, to my ears.

Because it's not a ML experiment, but a Max/Msp sketch which semi-randomly fires off carefully (by a human) prepared samples.

Well it's not AI or ML really - it's hand-picked algorithmic composition with additional contributions from human composers.

The holy grail AI composer would be able to generate unique, creative, well-crafted material on demand. Almost every system that has existed thus far generates mostly nonsense, but the results are tweaked or hand-selected by humans. Those that don't hand-select are the ones that sound algorithmic and computer-generated to anyone with remote music ability. That's why the current state-of-the-art in on-demand music generation sounds like elevator music - and to a trained musician you can still tell there's something "off" about it (Jukedeck, etc.).

Jukedeck[1] can produce some interesting results that are a little more harmonically interesting than a lot of simpler systems.

1: https://www.jukedeck.com/