The speaker begins with a strange, quiet image: waiting "like a guitar" for "the sacrament of an ear." A guitar only becomes music when someone listens, and the word "sacrament" makes that listening feel almost holy. The speaker seems to want to be truly heard, not just noticed.
The second half turns to a moth, and the title suggests the speaker is a kind of moth-collector, someone who pays close attention to small, easily overlooked creatures. Yet the lines say "nobody can tell / the truth of a moth / lost in the busy night." The moth's real nature slips away in the dark, and no one can fully pin it down. "Tell" can mean both "recognize" and "speak of," so the line works in either direction.
The mood is hushed, patient, and a little lonely. The poem links the speaker's longing for a listener with the moth's hidden life, as if both are waiting to be understood.