This is very old thinking (like half a century old) and the folks most qualified to comment on what is music and what is isn't are those at the vanguard, the "noise music" folks, the electroacoustic artists.
For one thing, monophonic music can be very rich. The Indian classical traditions (Hindustani and Carnatic) are both primarily monophonic. The "monophonic is boring" comment would also insult Bach (ex: suite for solo cello, which is awesome)
The article said monotonic music is boring, not monophonic music..
Monotonic means one tone - I.e. a sound that is made up of a single frequency. About the only time you'll ever here monotonic sounds is from a signal generator that is producing pure sine waves. The sound is very flat, lacks character and is, well, boring.
All real instruments, even a tuning fork, produce a multitude of sounds for each note. The number and intensity of the overtones each instrument is what makes the instrument sound like it does. Cellos produce rich overtones and are far from monotonic.
This is all clearly explained in the article. You do, however, have to read past the first paragraph...
Apologies for misreading the reframing of "monotonic". I only skimmed the article 'cos i'm familiar with the domain and the ideas expressed in it. It doesn't help that the article hijacks a common term in music for the special purpose of talking about pure sine tones. The rest of my comments hold.
For one thing, monophonic music can be very rich. The Indian classical traditions (Hindustani and Carnatic) are both primarily monophonic. The "monophonic is boring" comment would also insult Bach (ex: suite for solo cello, which is awesome)