When the key changes for a longer period and a new tonic is firmly established, we call it modulation. However, what do we call a very brief change of at most several measures, when harmony from another key brings the color of that key, but not strongly enough to make the listener forget about the original tonic?

Examples when this happen might be a secondary dominant (or several secondary functions), or modal interchange. E.g. if in the key of C we hear a progression A7-Dm, then followed by a progression in C, we likely interpret A7 as a secondary dominant. We hear it as borrowed from the key of Dm. I understand calling this modulation would be incorrect, but is there a more appropriate (and widely used) term?


The most common term is tonicization.

For example:

Tonicization is the process of making a non-tonic chord temporarily sound like tonic (SOURCE)

In music, tonicization is the treatment of a pitch other than the overall tonic (the "home note" of a piece) as a temporary tonic in a composition. (SOURCE)

Tonicization occurs when a chord or short succession of chords are borrowed from another key in order to emphasize—or tonicize—a chord in the home key. (See analyzing applied chords.) Modulation occurs when a longer succession of chords emphasizes a new tonic, leading to the perception of a new key. (SOURCE)

  • Jazz musicians usually refer to a tonicization as the "key of the moment" – Tom Serb May 7 at 22:38
  • @TomSerb I've been a jazz musician for several decades and have never heard that. Maybe a local expression? – Aaron May 7 at 23:24
  • it could be. Except for a brief NY stint in the early 80s I've only worked in the midwest – Tom Serb May 9 at 18:49

See, there are two types of "brief changes in key" that we see in western music. When the harmony "changes key" (usually via secondary dominants), it is called "tonicization". When the scale used in the melody changes, while the harmony remains diatonic (i.e. a piece begins to play notes from the G major scale over a tonic chord in C major), it is called a "scale mutation". Scale mutation is generally a term used to describe older music, specifically from the Galant Era. It was a term introduced by Giorgio Sanguinetti, I believe, in his amazing book on The Art of Partimento. Although the term is generally used to describe older music, I feel that it applies well to various other types of music, and is even more common in post-Galant-era music.

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    I've only ever heard "mutation" used in the context of medieval music, but not in the way you've defined it here. Can you point me to a resource where I can read more? It doesn't seem like this would actually change the key, but I have to allow I'm just not familiar with the term. – Aaron May 7 at 3:03
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    What do you mean by using G major scale over C chord? Do you mean playing C lydian scale, or rather indeed G ionian (same notes, but different tones are stressed)? – user1079505 May 7 at 3:05
  • Aaron-- You're right. Scale mutation is generally a resource used to describe older music, specifically from the Galant Era. It was a term introduced by Giogio Sanguinetti, I believe, in his amazing book on The Art of Partimento. It doesn't truly change the key, but tonicization does not either. If we tonicize G, we have not modulated to G, we are simply using a secondary dominant to lead to a G dominant seventh chord. If we mutate the scale used in the melody to G Ionian, we have not modulated to G either, we are simply changing the mode for a brief period of time. – Peter May 7 at 14:10
  • user1079505-- I was essentially describing a switch in mode. If we are playing a dominant chord in C Major, we can mutate the scale by playing a G Ionian scale over it instead of the usual C Ionian. – Peter May 7 at 14:12
  • Your previous comment clarifies your intensions. Consider editing your question to include some elaboration along those lines — comments are sometimes deleted. – Aaron May 7 at 19:14

Secondary, Borrowed or Altered chords

Secondary chords are a type of altered or borrowed chord, chords which are not part of the key the piece is in. They are by far the most common sort of altered chord in tonal music.[2] Secondary chords are referred to by the function they have and the key or chord to which they function. Conventionally, they are written with the notation "function/key". Thus, the most common secondary chord, the dominant of the dominant, is written "V/V" and read as "five of five" or "the dominant of the dominant". The major or minor triad on any diatonic scale degree may have any secondary function applied to it; secondary functions may even be applied to diminished triads in some special circumstances.


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