The Difference Between Change of Key and Modulation

Abstract

Presently, higher music education in Thailand faces numerous challenges. These include the development and implementation of teaching methods, the availability and use of instructional media, the provision of adequate teaching equipment, and access to reliable and accurate knowledge. Among these, a particularly significant issue is the translation of specialized musical terminology from English into Thai. Such terminology is widely used in courses on music theory that follow the concepts of the tonal era or traditional harmony. Difficulties arise when these specialized terms are translated in ways that lead to misunderstanding, confusion, or misinterpretation of the original concepts, potentially affecting both teaching and learning outcomes. This problem remains one of the most overlooked yet crucial aspects of music pedagogy in Thailand. Therefore, this academic article aims to provide a renewed understanding and clarification, supported by relevant examples and explanations, of the true meanings of the terms “change of key” and “modulation.”

Based on textbooks and teaching materials used in music education in Thailand, the term “modulation” has consistently been translated as “change of key.” This translation, however, is inaccurate and does not reflect the true meaning of the term. As a result, it has led to misunderstandings, even in compositions that employ parallel key relationships between major and minor modes, which are sometimes mistakenly considered part of modulation techniques due to the differing key signatures of the two modes. In reality, the correct meaning of modulation refers to a shift of the tonal center—that is, a change of the key center or tonic that establishes a new tonal area.

Therefore, it is important to clarify the concept of “modulation.” For example, in the keys of CM and Cm, although these two keys have different key signatures, they share the same tonal center or tonic on the note C, without moving to a different tonic. This relationship is referred to as “parallel keys,” which involves only a “change of mode” or “modal mixture.” In contrast, CM and Am share the same set of notes and key signature but have different tonics. This represents a shift of the tonal center between “relative keys,” whether moving from major to relative minor or vice versa. Similarly, consider the tonic between BM and CbM. In these cases, the tonic is spelled differently and the keys have different key signatures. These are referred to as “enharmonically equivalent keys,” which do not constitute a shift of the tonal center, since the listener still perceives the same mode on the same tonal center, only spelled with notes from a different key.

There are three principal types of shifts of the tonal center or tonic: 1) relative keys, 2) closely related keys, and 3) distantly related keys. Parallel keys and enharmonically equivalent keys, however, do not constitute shifts of the tonal center under the definition of “modulation.” The pivot chord that occurs during a tonic shift—a triad that exists in both the original and the new key but functions differently in each—is specifically referred to as a “diatonic pivot chord.” Furthermore, shifts of the tonal center can occur only to major or minor triads. Diminished and augmented triads cannot support a shift of the tonal center due to the absence of a key based on these triads.

When determining whether a composition involves a key shift, one should rely on listening to the piece, as perception may differ. Some listeners may perceive the new tonal center long enough to assert that a modulation has occurred, while others may experience it only briefly and consider it a “tonicization.” The identification of the “point of modulation” and the number of pivot chords may also vary. Such differences in analysis are not critical, as they depend on the individual’s informed judgment and interpretation. Many compositions do not change the key signature even when a tonal center shift occurs. However, key signature changes can occasionally be observed between phrases or sections. Furthermore, in a musical movement where a new key is indicated, this represents merely a change of key to establish a new tonal center, rather than a shift of the tonal center in the sense of “modulation.” Clarifying this distinction ensures greater precision in both teaching and analytical practice.