At the Shinjuku Bunka Center, Antonio Enzan Olias plays an Edo period shakuhachi made by Chikujin, and Etsuzan Fujiyoshi plays a shakuhachi made by his Sensei Takahashi Kuzan (1900-1986) These are both 1.8s pitched in C#. Higuchi Taizan's main flute was also a C#. My teacher Morimasa Seisui Horiuchi prefers the 1.8 C# and has two fine examples, including a two stamp shakuhachi made by his teacher Tomimori Kyozan. Tanikita Muchiku also favored the C# as many other great Masters of the Myoan lineages.... My favorite flute is also a 1.8 C#, and Mori-san and I predominantly play this pitch 90% of the time in lessons, after an occasional break with 1.8s or shorter, pitched in D.
Why this preference for C#? It is said the Consciousness Chakra resonates with the musical pitch of C#, verbalized as OM. The sound of OM connects us to the universe in a very real way. OM is derived from the Earth’s rotation around the sun. It takes 1 year, or 31556935.97 seconds, for the earth to complete one cycle of rotation. If frequency is cycles per second, you get 1/31556935.97; the portion of a year that exists in one second. The frequency of C# is at 136.1 Hz, OM. Many have said shakuhachi is the sound of Earth. It's interesting to see the pitch reflected in the orbit sound of our planet, from the the roundness of the root, the endless enso of the bore, taking the listener in its grounded sound circling through the space of OM