Johnson explains the title's use of the trombone by discussing the vocal and rhetorical qualities of a preacher he had recently heard who, he felt, exemplified the compelling and persuasive nature of the folk preacher, naming the trombone as "the instrument possessing above all others the power to express the wide and varied range of emotions encompassed by the human voice — and with greater amplitude."
Johnson employs the trombone as a metaphor for illustrating a preacher’s vocal and rhetorical attributes, emphasizing its capacity to convey a broad spectrum of emotions—along with greater intensity—similar to that of the human voice.