The American auctioneer is an improvising musician whose practice both directs and is shaped by the actions of the bidding audience in a participatory musical performance. The rapid, often unintelligible chant of the auctioneer represents a sophisticated set of musical skills employed for the purpose of economic transaction. This dissertation examines the musical and improvisatory practices of the auction chant, or bid-call, through analysis of pitch, melodic structures, rhythm, and meter as functions of an oral formulaic and creative process. The study draws upon ethnographic, archival, linguistic, and cultural studies in order to assess the extent to which discrete musical characteristics of the chant serve the socio-economic purposes of the auction. Auctioneers' embedded musical and linguistic patterns are acquired through a practice-based pedagogical method and are treated flexibly such that the chant remains unpredictable and exciting to the listener. While the monotone chant serves as the foundation of the bid-call, auxiliary pitches (most often pentatonic or major scale subsets) offer melodic variety and function in a fulcrum relationship to the "hum." Likewise, auctioneers establish a "referential" meter wherein a single metrical organization of the pulse returns repeatedly, alternating with expansions or contractions of that fundamental meter. Listeners are entrained to expect musical consistency, but through disruptions of familiar musical patterns, the auctioneer focuses bidder attention on the chant rather than the realities of the economic transaction in progress. Ethnographic research with auctioneers throughout the United States and archival recordings of live auctions dating back to the 1940s reveal that many characteristics of chant practice are shared among auctioneers; however, stylistic practices vary based on sales type (livestock, real estate, agricultural equipment, estate, etc.). In all auction types, the bid-call offers a heightened emotional experience for the attendees and an opportunity for audience participation and musical agency.