Whether or not mantra within the context of Theravada can be applicable would rely in your intention with it, IMHO.
If it aids in your consideration, mindfulness, focus, and attaining Jhana, I really feel it very applicable. Once more, it’s a assist, a innocent means to an supposed finish.
It might be inappropriate, conversely, in the event you supposed a number of the claims that some Mahayanist, or Hindus, and others attribute to them.
A number of the very straightforward and conventional mantras taken kind Sanskrit seed syllables, and in addition adopted by Tibetan Vajrayana Buddhists are “Om”, “Ah” “Ho” and “Hum”.
Once more, your understanding, and intention, determinate their use.
For instance, taking “Om” as representing the Yogic hyperlink between Brahma and the Atman will surely be misguided for the Theravada Buddhist.
Nevertheless viewing it a merely a sound that you simply produce as an support in meditation is altogether acceptable. Simply as one would observe the breath, even the breath energies within the physique as one of many means of accomplishing Jhana, additionally following the breath on the inhale, and the “Om” sound on the exhale, with it’s vibration inside the physique is a wonderful means.
The necessary level is then, as with breath meditation to observe it attentively and constantly, coming again to it once more, and once more, as a body of reference for the eye.
I exploit it. It really works nice. I discover much less bother with intrusive ideas, Jhana is discovered simply, and is extra simply sustained.
A Theravada utilizing Budho for a similar finish may simply go astray considering the repetition was bringing him union with The Buddha, Prompt enlightenment, or every other unrealistic end result.
So long as you perceive it’s use in your meditation, and preserve it in consideration to that finish, all is nicely.