The word umami sparked a bit of discussion in the comments to my last post, and since I stumbled across it again in an unrelated document I thought I'd beat the dead horse a little longer.

So, the document in question is Hitorigoto 独言 ("Talking to myself"), by Hisamatsu Fūyō 久松風陽. Fūyō was the fourth head of the Kinko-ryū school of shakuhachi, and Hitorigoto is advice in point form for members of the school. It was written in 1818, only a few decades after Hanzan's work.

初心より美敷（うつくしき）音のむまみ（旨味）を修行すべからず、音艶むまみは出来るを好んで出かすを嫌ふ

As a beginner, do not strive for the (m)umami of beautiful sound. It is pleasing when polish and (m)umami emerge from (dekiru) the sound; to force them out (dekasu) is disagreeable.

In other words, don't try to get a beautiful tone out of your instrument. Just pay attention to the tone you do get, and before long it will become beautiful. (TL;DR: Watch the path, not the goal.)

What does umami mean here? I would argue that, again, it represents some truly and deeply satisfying quality in a performance, something that cannot be faked or forced but must grow organically within the performer before it can be revealed. It's not even necessarily about beauty. Umami might manifest as an abrasive or challenging quality. Truth and meaning are what matter.

Bonus link: Another site that also has Fūyō's Hitori mondō 独問答 ("Questions and answers by myself"). Features this awesome exchange:

問 普化禅師はいかなる人ぞ
答 知らず禅家の知識に問へ

Q: What kind of person was Master Pǔhuà [Fuke] 普化?
A: I don't know. Ask a scholar at a zen temple.