Zen and Non-duality
In theory, at the core of Zen teachings there seems to be a message of non-duality. There is "only this", and there isn't anything that can be said about it. Famous stories in the literature commonly mention teachers who deny their existence and say that Zen has nothing to teach, no one to teach it, and no one to teach it to. Yet, there are apparently various Zen schools with different practices and teachings. There are people who call themselves Zen masters, and Zen students.
The apparent contradiction is that non-duality teachings, and practices that attempt to point to non-duality, are an impossibility. If there is "only this", there can be no practice to get closer to it. There is already "only this". If there is "only this", then there is no space or time to get closer in. There is "only this". If there is "only this", there is no one to understand it or misunderstand it, to get it or not get it. The illusion of getting it or not getting it is also "only this". It is impossible to find some state of enlightenment or non-duality when non-duality or "only this" is all there is already.
Any religion, teaching, or practice is necessarily pointing to separation rather than non-duality. A teaching assumes a teacher and a student. A practice assumes someone with something to do, and somewhere to go that is not already here, or something to attain that is not already this. So the attempt to teach or practice actually obscures non-duality. The practitioner attempts to get somewhere that he or she is not already, when in fact there is nowhere other than this. This contradiction seems to be acknowledged in Zen literature, where it is commonly said that neither effort nor non-effort will help. There is nothing that can be done.
Zen practices such as zazen, suizen, and koan contemplation can be great for increasing well-being and happiness, decreasing suffering, for better health, and for coming to profound realizations, though in reality for no one. However they cannot lead to the message at the core of Zen, "only this", to what is already, since there is already "only this".
Shakuhachi and suizen can apparently be done as a practice, but in reality there is "only this", seemingly appearing as blowing a shakuhachi. There is nothing that needs to be done, can be done, or is being done. Only this. Perhaps some of the Komusō (虚無僧 - illusory nothing monks), the monks who created the shakuhachi, honkyoku, and the suizen practice, attempted to allude to this in their name.
In zazen the practice generally begins with sitting comfortably upright, usually on a meditation cushion, breathing naturally through the nose, becoming aware of breathing, and keeping attention on breathing. When attention wanders to sounds, sights, thoughts, or other sensations, it is gently brought back to breathing. In some schools of Zen, shikantaza, just sitting with open awareness, is practiced instead of or after a student is able to maintain attention on breathing for an extended period.
The practice of zazen is beneficial for both physical and mental health, and can lead to a deep sense of well-being. However the purpose of the practice in Zen is not for health or well-being, but to transcend the conventional experience of self, to the realization of no-self, nothing, or emptiness. The contradiction is that there is no self to transcend in the fist place, and the practice of apparently sitting a self down to discover that there is no self to sit down makes no sense at all. The idea of a practice with a goal can apparently hide what is looked for, since what is looked for is what already is. Nevertheless, "only this", or nothing, can appear as practicing zazen with apparent benefit.
The practice of suizen (blowing meditation) with a shakuhachi traditionally has the same aim as the practice of zazen (sitting meditation). The shakuhachi honkyoku phrases are based on the breath, and the breath, the sound that it creates, and the silence between phrases can be the focus of attention. If attention wanders, it can be brought back to the sound. With practice it can be revealed that the sound arises nowhere, no-when, and for no one. There is simply sound arising. A shikantaza approach can also be taken, with "just blowing" and open awareness.
Suizen practice is also beneficial for health, and there are additional benefits from the breathing patterns embedded in honkyoku. Again, the contradiction is the idea of a self practicing suizen to discover that there is no self practicing suizen. Nevertheless, "nothing" can appear as practicing suizen with apparent benefit.
Ultimately, non-duality is a mystery that is not possible to understand. There is nothing to understand and no one to understand it. Below is a song with my 2.6.7 Ikegami shakuhachi, and the voice of Jim Newman, who gives talks on non-duality.