What do you mean by playing "without harmony"? Using a pedal tone, which Coltrane got into after a period of very dense harmonic playing. He would use one or two harmonic references throughout a song, as he did on "So What" [from Miles Davis's Kind of Blue, on Columbia]. It was basically D for sixteen bars, E flat for eight bars, and then back to D. Ultimately, he worked with only one harmonic reference point, and then in "Ascension" [from Best of John Coltrane: His Greatest Years, on Impulse] there was nothing harmonically.