The 3389 copper (alloy) bells from the offerings included in successive building phases of Late Postclassic Templo Mayor (A.D. 1325-1520) of Tenochtitlan (Mexico City) are the results of production processes influenced by social, economic, ideological and technological factors. The compositional and morphological variability of the bells in the early construction phases of the Templo Mayor suggests the presence of several workshops in or around Tenochtitlan, while the reduction of the spectrum to one bell type made of copper-tin bronze, points towards a standardization of the production process and a decrease in the number of workshops that supplied the Templo Mayor in later phases. The compositional and morphological information, as well as contextual analysis and comparison with other Mexican bells, give insights into the bells’ symbolism, the mechanisms used to supply the temple with offerings, the organization of metalwork and the rationale behind some of the technological choices for the artisans. The detected changes through time (seem to) point to important shifts in the ideological, economic, social and technological influences on the artisans’ choices in the latter half of Aztec rule.