If we read the Wikipedia page for musical key, or the question about the Definition of minor key, we might notice conflicting views regarding the definition of "key".

On one hand, we have a view that only tonal music is "in a key", and modal music is not tonal. If a song uses the natural minor scale only and has the tonic on the scale's first degree, it is in fact not in any key at all, it is in the Aeolian mode. If I understood correctly, some meanings even require the existence of not only the leading tone but its tritone as well, so you must have a V7 chord and a plain V wouldn't be enough. Or otherwise, a piece of music with a tonic of F, and F and C major chords but no C7 and no Bb note, leaves the door open for perhaps being in F Lydian and therefore modal and not in a key at all.

For example in this well-known pop song (ear worm warning!), there's no leading tone, and in the main part the chords are just Am - Dm - G - G.

But on the other hand we have opinions saying that if you have a tonic note, that's your key. If the home chord is a minor chord, it's that note's minor key. And whatever other notes you use, doesn't matter at all. You might use harmonic, melodic, Dorian, whatever, you're in the same key. In this sense, it would be completely ridiculous to claim that "Live is Life" is not in the key of A minor.

Are there clear and commonly used names for these definitions? In my opinion, the simultaneous usage of multiple different definitions of such an elementary concept as key, even changing back and forth inside the same page like what we have on the Wikipedia page, causes unnecessary confusion. I'd like to be able to point out and refer to the different definitions like "According to the _________ meaning of key that's used in _________ contexts, you need to have a leading tone, but according to the _________ meaning that's used in _________ contexts, you don't."

(I think I already know an answer or at least a suggestion to this, but I'd like it to be an explicit referrable question on this site.)

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    Other examples might include the Blues, which usually places dom 7th chord on the I, IV, and V but uses the minor pentatonic (MP) or Blues scale = PM + b5 on I. Also, miles Davis' So What which is modal in D dorian (with a change to Eb Dorian) but we don't say it's in the key of C. – ggcg Jan 2 at 16:39
  • It might be that the use of key is too restrictive in some cases, or does not describe all of western music. Also, we use keys for convenience in writing SMN in that we may pick the "key" that leads to the cleanest notation. – ggcg Jan 2 at 16:40
  • @ggcg Maybe if you just say that So What is "in D", leaving out the word "key", then it's politically correct and avoids taking sides? ;) – piiperi Reinstate Monica Jan 2 at 16:46
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    Modal music in the modern sense of the word is tonal in the sense that it definitely has a very clear "home chord". So in any case it would be ridiculous to claim that that song is not in A minor. I don't think that anybody would seriously claim that we can't define a key for that song (or similar ones) just because we don't have a leading tone. Lots of pop songs would be keyless otherwise (even though in almost all cases we can clearly hear the "home chord")! – Matt L. Jan 2 at 18:58
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    "One would use harmonic or melodic minor to truly be in a minor key": that comment is really quite off the mark, at least taken out of context. Most tonal pieces in a minor key will use both the raised and lowered sixth and seventh degrees in some place or another. Real music in minor keys does not generally stick to one version of the minor scale; the only place where you do that is when you're practicing playing scales. – phoog Jan 3 at 1:50

I would recommend Brian Hyer's famous chapter "Tonality" in The Cambridge History of Western Music Theory. In it, he lists eight uses of the term tonality; I'll highlight just a few:

  1. An adjective indicating "the systematic organization of pitch phenomena in both Western and non-Western music" (727). He goes on to say that this applies to the ecclesiastical modes, Indonesian gamelan, Arabic maqam, Indian raga, major and minor scale collections, etc.
  2. "Tonal" as used as opposed to "modal" and "atonal."
  3. But, premodern music can be understood as "tonal" based on the grounds of (1) above.

Thus it seems to be that the use of "tonality" is context-dependent, and there isn't a robust system for differentiating among different systems.

With this in mind, I'll highlight a quote from Hyer about Harold Powers and his famous article "Is Mode Real?":

Powers has even argued that modality and tonality coexist as musical properties on separate epistemological planes, in which case it is meaningless to imagine a transition from one to the other; modality and tonality in this sense are no longer competing or mutually exclusive means of musical organization. (738)

You're correct that, at least historically, "tonality" related to the tritone and the dominant seventh. Alexander Choron in 1810 was the first to use the term "tonality," actually pinpointing the exact moment that tonality came into being with the use of a dominant seventh in a Monteverdi madrigal around 1590 (!). (François-Joseph Fétis, both as a teacher at the Paris Conservatory and an author of various publications, then popularized the concept of tonality around 1840.) But I sense that that specificity is no longer in play today.

Depending on what you're saying, however, you could conceptualize tonality in different ways. Again quoting Hyer: "Choron, who emphasizes relations between harmonies, [differs from Fétis, who] places more stress on the order and position of pitches within a scale" (733). This then leads to the future distinction of "functional theories" by theorists like Rameau and Riemann compared to the "scale-degree theories" of Weber, Sechter, Schenker, etc. Depending on the conversation you're having, that could be a worthwhile distinction to make.

  • "popularized the concept of tonality around 1840": what was Bach going on about, then, with the 48 preludes and fugues? Tonality may not have been popular as a term in his day, not it was certainly a widely understood concept. – phoog Jan 3 at 1:41
  • This is a great answer, but I feel that it may answer a different question. :) I was trying get something concrete for this idea that using the word key implies a certain flavor of tonal (as opposed to modal) music where you have a leading tone etc. :) Maybe I should add more categories, because the two definitions I listed are not the only ones out there, there's apparently also a view that "a key is a scale", which is blurted out right at the start of the Wikipedia page. That one is also occasionally implied when people talk about "notes outside the key". – piiperi Reinstate Monica Jan 3 at 19:57
  • @piiperiReinstateMonica the problem is that "key" doesn't imply a leading tone unless you define it that way for the purpose of a particular discussion. From the practical point of view, a group of musicians playing a piece with an empty key signature and no accidentals with a tonal center of A will say that the piece is in the key of A minor. – phoog Jan 4 at 17:20
  • @phoog It is unquestionably so, most of the time anyway. What I'm trying to ask here is, if you had to label that particular way of using the word "key", what would you call it. And where, which context, which cultural time and place does it originate. There are other meanings, for example the "key = scale" thing, which I consider a harmful idea that doesn't account for actual music and Real Life, but which has nevertheless made its way on the Wikipedia page and keeps appearing on this site as well. – piiperi Reinstate Monica Jan 4 at 17:27

Are there clear and commonly used names for these definitions?

I don't think there are completely definitive terms for the various usages, but the following is usage I have seen:

  • Church mode for Medieval chant
  • major key / minor key for common practice period, the "major/minor system" using tonic/dominant harmony. the other usage is a kind of generic diatonic, usually pop music, where the key indicates the tonic chord, but the harmony isn't necessarily tonic/dominant. These two usages might seem confusing, but the context is usually clear. If someone says a U2 song is in A major, I expect A major to be the tonic chord, etc. etc. but I don't necessarily expect tonic/dominant cadences and such. It isn't too hard to wrap your head around two different harmonic styles used to define a tonic chord and calling that "in the key of..."
  • "color of", "flavor of" phrygian mode, etc. in jazz/rock/folk, but this usage is in classical style too with terms like phrygian cadence, or saying the Neapolitan chord has a phrygian feel, basically it's the major/minor system with certain altered scale degrees having modal color.
  • By number, ex. Mode III is phrygian, Medieval chant
  • "mode of a scale" seems to be a modern concept, jazz/rock/etc. like 'the altered scale is the seventh mode of melodic minor ascending.'
  • this "mode" for that chord is a jazz concept, the usage treats mode and scale as basically synonymous and it's always that a mode/scale is some kind of embellishment of a chord and not a tonality

That list certainly isn't comprehensive, but I think it gives the sense of context for usage in many cases.

The case that seem "problematic" to me is pop music with alternating tonal centers and indefinite formal structure. All the tones to give a key signature will be present, many of the chord progressions will be conventional, a clear tonic will be present, but a tonic/dominant progression will be absent. Often the melodies are pentatonic or in some way don't use a leading tone. The music is groove based, often repetitious, in recordings there is often a fade out implying there is no formal ending. In a certain sense to define a "key", really a tonic, for such songs, is to imply an end point, and that is antithetical to the style. The problem is not really about the definition of "key", it more a matter of form and a infinitely repeating structure.

Using the song Live Is Life I suppose you could say it's in the "key of zero sharps/flats." From that we know what the palette of tones and diatonic chords is, but the tonic remains indefinite. It's a clumsy, unsatisfying wording, but I've never heard any standard wording. Usually it's music theory wonky argument over C major, or G mixolydian, A aeolian, D dorian, etc. that misses the whole point of the indefinite structure. Or, better yet, just say what it does: alternates between G major and A minor. Isn't that perfectly descriptive?

Below are a few readings on the concept of "key" that grabbed my attention in the past:

From Gjerdingen, Music in the Galant Style

Part of the difficulty resides in the word "key." By the second half the century—Clementi's time—the meaning of "key" was approaching its modem sense, as in "the key of Bt> major." In the first half of the century, "key" could also imply a note in a scale that received some temporary focus, as in "G—the sixth key in the hexachord on Bb." If we examine a repertory from the first half of the century, we ought to find more of the practices that were not yet "obliterated."

I mistakenly thought the following was said by Bartok, but it's from Halsey Stevens, The Life and Music of Bela Bartok, analyzing Bartok's music:

tonalities...are handled so freely that one is justified only in saying that they are "on"--not "in" this or that tonality....by this it is understood that these keynotes serve as orientation point: that the music is organized around them, modally or chromatically, freely fluctuating, using the keynotes as points of departure and points of repose...

Atcherson, Key and Mode in Seventeenth-Century Music

There isn't a particular quote that stuck with me. It's just twenty pages of detailed discussion of key and mode. He gives a nice bulleted list of "modes vs. keys" with items like: ambitus is an important aspect of mode definition and identification, but irrelevant to the concept of key. He really tries to explain the difference in technical terms. Of course "mode" in this case means mode like Gregorian chant, not the jazz usage of mode.


In the resources immediately available to me, key is consistently associated with mjor/minor tonality.

key. 1. As a compositional principle, the adherence in any passage to the elements of one of the major or minor scales, or tonalities.

The Oxford Companion to Music, ed. Alison Latham (Oxford University Press, 2002).

Key. (1) The quality of a musical passage or composition that causes it to be sensed as gravitating towards a particular note, called the key note or the tonic. One therefore speaks of a piece as being in C major or minor. See Tonality.

In The Complete Musician (2nd ed., Oxford University Press, 2008), Steven Laitz never defines "key", and tends to use it in ways defined by context. However, its first use in the book comes in the context of defining "key signatures" (page 11) and strongly associates it with the tonic of a major or minor tonality.

The key signature ... presents a pattern of either sharps or flats that is a helpful musical shorthand for conveying pitch classes of a key.

Aldwell and Schachter in Harmony and Voice Leading (2nd ed., Harcourt, Brace, Jovanovich, 1989) also do not give a specific definition of key, but they do connect it to major and minor tonalities.

The key-defining function ... is connected with the fact that any particular diminished 5th or augmented 4th occurs in only one major key.

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    I'm not sure what you're suggesting as the names. Are you saying that a definition of key where e.g. modal leading-tone-less music is not said to be in any key at all, has never even existed anywhere? – piiperi Reinstate Monica Jan 2 at 19:39
  • @piiperiReinstateMonica I took the question to be specifically about nailing down a definition for "key". According to the sources I looked at, "key" is specific to tonality. For modality I suppose one could use "pitch center" and "mode". – Aaron Jan 2 at 19:41
  • Ok. In the question I assumed that there's a modern de-facto practical, more relaxed meaning for "key" which doesn't demand a strict separation between tonal and modal styles, and where you could call any tonic as being a key center, even if someone might argue that the music is modal. And that there would also be this other meaning where some types of music just is not in a key at all. And that these two interpretations could be assigned simple names. :) – piiperi Reinstate Monica Jan 2 at 19:44
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    @piiperiReinstateMonica IMO, the de facto usage (the way I use it, anyway) is that "key" = "pitch center" + "mode". So, I speak of the "key" of "G Mixolydian", for example. – Aaron Jan 2 at 20:16
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    @phoog I'm suggesting that that kind of a view appears to exist at least in some contexts, but it's unclear to me where exactly that view comes from. With this question I was trying to find a clear, referrable name for that interpretation of "key". – piiperi Reinstate Monica Jan 3 at 13:04

Examining the "Life is Life" chord progression from the verse, it is clear that it uses exactly all the pitches of A minor (equivalently C major, or any of its modes):

  • A minor: A - C - E
  • D minor: D - F - A
  • G major: G - B - D

This is enough information to determine the key signature that one would write when transcribing (that passage of) the song. So in that weak sense of "key", the matter is simple.

However, in the slightly stronger sense of "key", some note (or chord) would have to function as the "home chord" or "tonic pitch". When we look at this side of things, it's more a matter of degree than a simple yes/no question.

Here are some of the signs that one chord is playing the role of tonic/home chord:

  • Tense intervals in other chords resolve to an interval of the home chord regularly, effecting some sort of closure. In the case of A natural minor, one would expect a resolution of the tritone B - F resolving to the major third C - E (which occurs as part of A minor, which is A - C - E). (This feature seems mostly missing from "Life is Life", since the G chord lacks the F, and the singer is not touching that note either.)

  • The piece starts and/or begins with the tonic/home chord.

  • The tonic/home chord often occurs at the end/beginning of phrases.

So you are right to point out that "Life is Life" is not a super prototypical example of a song that's strongly in the key of A minor, by the above criteria. So perhaps one could say that it is in the key of A minor, but without very strong tritone tension/release towards the home chord. The fact that A minor is the first chord of a repeating cycle supports the idea that it would be the key of the song. The only alternative would be G mixolydian, if you hear G as the home chord. It's equivalent, except for the choice of home chord.

This last impression is perhaps confirmed by the 'cyclical' feel of the chord progression of "Life is Life". Neither of the chords feels particularly 'home' to me. It's mainly a groove that we want to keep repeating. This is not atypical of contemporary pop music. Daft Punk's "Get Lucky", for example, just cycles between Bm - D - F#m - E. None of these chords are very tense in the sense of tritone resolution, and you can probably hear several of the chords as "home" if you wanted. What is however not subjective is the fact that the progression uses exactly all the pitches found in A major. Most theorists agree that it's in B dorian.

  • Daft Punk: I don’t think you mean dorian – user71850 Jan 3 at 16:34
  • thanks, I meant B dorian, not D dorian. B dorian makes sense with the progression. – ScienceOfLogic Jan 4 at 17:09

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