Guidonian solmization was adapted to 18^th-century tonality in the context of Galant solfeggi. The medieval and Renaissance solmization first articulated by Guido of Arezzo accommodates the diatonic system of chant, which involved eight notes, G-A-B-natural-C-D-E-F, and B-flat (B-flat is a diatonic pitch; a kind of get-out-of-tritone-free card). I show how Guido’s solmization system and the eight-note diatonic system have a reciprocal relationship: solmization evolved to accommodate the idiosyncrasies of the diatonic system, and subsequent composition evolved to take advantage of some of the affordances of this solmization system.

Hexachordal solmization gave way to seven-note solmization in many pedagogical traditions around the same time as the circle of fifths was first articulated. As the tritone was recast as a feature of the diatonic system rather than a bug, the need for overlapping hexachords was obviated. In this period, solmization syllables were repurposed to be synonymous with either letter names (fixed-do) or scale degrees (moveable-do); much of their original utility was sacrificed in the process.

Galant solfeggio straddles the older hexachordal system (designed for a now-defunct diatonic system) and the newer tonality (where fifth relations remain paramount, but the diatonic system is recast as a “closed” circle). Galant musicians found a simplified version of hexachordal solmization useful for articulating the similarities between melodic gestures in tonic and dominant, for navigating the proximity of a major key and its relative minor, and for developing a repertoire of improvised ornamentations.

I argue that hexachordal solmization is pre-adapted to describe several basic tonal behaviors: the close relationship of tonic and dominant and the potential to modulate by fifth. But I will demonstrate that solmization does not motivate these aspects of tonality; rather, Guido was articulating something more fundamental about diatonic space (that fifth-related pitches behave in similar ways) that tonality would eventually take advantage of on both local and global levels.

In the Renaissance, solmization was used to make themes sound different through the use of inganno, but beginning in the 17th century, it was invoked to explain how themes could sound the same even when altered by what we call “tonal answer.” In this talk I will contrast these two uses of solmization, both of which depend on the multiple names that could be given to notes based on the semitones surrounding them.

Examples from Gioseffo Zarlino, Angelo Berardi, and Gregorio Strozzi show how inganno allows the composer to invent variations on a theme by maintaining the syllable names of the notes but, by switching hexachords, not their pitch classes. The varied tunes can sound almost entirely different.

On the other hand, solmization could be called upon to explain why imitative entries altered to accommodate the modal octave could be considered the same. I will illustrate this with examples from Giovanni Bononcini, Johann Prinner, and Johann Fux. Surprisingly, this method of explanation survived into the 19th and 20th centuries in writings of Heinrich Bellermann and Arnold Schoenberg, who substitute “key” for the older “mode” but retain hexachordal terminology.

The dissemination of galant music in European colonies offers unique archival evidence. As Sánchez-Kisielewska (2016) shows, galant schemata can serve as markers of the dissemination of the galant style into the new world through the works of Ignacio Jerusalem and José de Nebra. In critiquing the “colonial galant,” Grant (2022) mentions the coexistence of hexachordal and heptachordal solmization in the Jesuits’ colonization of Indigenous people in preset-day Bolivia. My talk relies on Lanam’s (2018) edition of the Vezerro de lecciones, a source from colonial Mexico: this source shows how Jerusalem participated in disseminating Italianate solmization teachings. This particularly lengthy and well-preserved manual reflects the practical “hidden theory” of this session. I argue that Jerusalem’s music making—though clearly tonal and galant—is particularly transparent in its relation to hexachordal solmization. I offer an analysis of Jerusalem’s aria “Todas puedan alegar” and of selected exercises from the Vezerro, exploring tensions between the mental model of hexachordal solmization, (which Jerusalem actively and explicitly transmitted), and galant schemata (i.e., part of the implicit knowledge of musicians at the time), arguing that both are central to his craft and pedagogy.

Recent applications of hexachordal solfege to classical-era music offer exciting avenues for analysis and performance, which could rightly be regarded as inspired by eighteenth-century practices. A more extreme claim put forth by various scholars is that these modern applications are not merely inspired by historical practice but directly reflect how eighteenth-century musicians solmized, thereby illuminating otherwise “hidden” musical implications. However, these extreme claims have not received the scholarly scrutiny they deserve. Closer examination calls into question the extent of the historical grounding of modern hexachordal practice as applied to Galant solfege, thereby placing its benefits and limitations in better perspective.

Recent studies on the hexachordal basis of galant schemata raise fundamental questions about the nature of diatonic space in the early-modern era. In short: should we interpret the enduring practice of hexachordal solmization in 18th-century Italy as pointing to a hexachord-based conceptualization of galant melody, as argued in Baragwanath 2020 and 2024, and IJzerman 2024? If so, should our analytic understanding of galant music be grounded on such hexachordal notion of diatonic space?

The answers to these questions hinge on the precise nature of the hexachord as a diatonic region. The current scholarly orientation reads the 18th-century solmization of the diatonic scale as an indication that the octave was regarded as the product of two overlapping hexachords. Having reached the dominant G-sol from the tonic C-ut, the singer would “mutate” to the “sharp” hexachord — G-sol becoming G-ut — to complete the scale.

However, to sing or to label the diatonic semitones with the same two syllables mi-fa is not a sure index of a hexachordal conception of diatonic space. While the continuing use of the ut-la syllables led 18th-century theorists to occasionally mention the “essacordo” as a scale, it may be misleading to take such references at face value, as they may have been the product of a cavalier approach to terminology or of the weight of disciplinary inertia, not of a hexachordal conception of diatonic space. Indeed, on closer analysis the solmization of the major scale indicates the diatonic position of the pitches only in part: C-ut is also fa because it has a semitone below that makes it eligible to be a “tonic.” On the other hand, G-ut, with a whole tone below, is also sol, the reason why it is heard as a “dominant.” In other words, the full diatonic placement and function of a diatonic pitch depend on its position within the octave, not the hexachord.

The suggestion of a hexachord-based method of analysis for galant music, introduced to usher in a historically informed understanding of that repertory, may paradoxically rest on an unsustainable reading of both historical music theory, and the harmonic foundations of the time.