Define mantra: a sound, word, or phrase that is repeated by someone who is praying or meditating.
Repeat, "A Love Supreme", and it takes on power each time. Mantra's are associated with Eastern religions such as Hinduism, which is the way John Coltrane was leaning at the time of his death.
If you absorbed the man and his music at this time in his life, you can truly understand what he meant when he said "All religions have a piece of the truth". Take that a step further and chant, "A Love Supreme, A Love Supreme, A Love Supreme", then stretch your imagination into it incorporating "All Religions", and you will have where Mr. John Coltrane was coming from.