To the aspiring church musician around 1700, the many ways of thinking about tonal structure in music must at times have seemed bewildering. There were the traditional eight modes; various incarnations of the twelve-mode systein; the set of keys arising from polyphonic psalmody; and an emergent system of only two modes, often still conceptualized in terms of solmization-based Ut and Re (or La) tonalities, that could each be situated on any chromatic degree. The young musician's task was made somewhat easier by correspondences between certain modal systems and musical repertories-such as that between the eight-mode system and plainchant-but such correspondences were hardly exclusive: some theorists, for example, thought there to be twelve modes in plainchant. It is plausible that four randomly selected musicians, asked to name the mode of a given polyphonic composition, might have invoked four different modal systems.