This is really well done. I find the default "free form" mode is by far the most interesting, and it's more complex than a lot of the comments are implying here. It cycles between different patterns, and the pattern is changed by inserting a space or punctuation. You can easily verify this by typing an extremely long word without spaces: the pattern becomes apparent, even though it's always transposed up or down by 5 semitones when it repeats. This interval is well chosen - it effectively explores all possible transpositions of the pattern, while keeping the transitions harmonious. This also means that the tonality is constantly wandering, there is no overall key but only transient tonalities.

Different punctuation marks provide different collections of more-or-less conclusive chords. This might be the only place where tonality is hinted at, especially if you bash the comma, you can hear it's rooted in one key for the whole session. As far as I can tell those special characters are / ! ? 1 . ,

I haven't figured out if the patterns are generated on-the-fly or chosen from a predefined set, but they tend to have a nice melodic quality.

Someone also mentioned special words rain and wind, but there are more... very fun to explore. The concept is nice but the execution is especially interesting.