Perhaps the most difficult thing to discover when I started playing the shakuhachi was finding where the sweet spot was; that spot where the space between my lips, through which I blow air, was right in line with the utaguchi. Finding this sweet spot – I don’t know if there’s a Japanese word for this term, but it is used frequently – is the key to being able to make sounds consistently.
Unlike with other instruments I have played – guitar, piano, and viola da gamba, where there is no such position that needs to be found – the relationship between my lips and my instrument is organic and changes daily, even from moment to moment, making it difficult to maintain this consistency. It changes according to the way I breathe, and according to the atmosphere: is the air humid or dry, affecting the lips, or is there pollen, causing my lips to swell a bit because of my allergies?
Another element I discovered fairly early on is the fact that I don’t blow from the center of my mouth. I had known from seeing myself in a mirror once, years ago, that when I whistle, the space in my lips is a bit to the left of center. If you’re new to the instrument, and are trying to find that sweet spot, whistle in front of a mirror; this may help you.
At first, I assumed that this was a mistake, but after watching videos of a number of performers, I have seen that it is not at all uncommon to blow from one side of the mouth. It’s quite visible in this still from a video of Fukuda Teruhisa, to the left. Not only does he blow a bit left of center, but when he plays meri notes, he tilts his head even further in that direction.
But finding and maintaining this sweet spot is the key to making consistent sounds, and the reinforcement of the lip muscles is essential to achieve this. (And ro-buki helps strengthen those muscles.) So this is a long process, but awareness of how to find the sweet spot and how it varies over time is essential.