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Roman numeral analysis uses capitalization to disambiguate Major from minor, so the paradigm is not entirely based on inference. There seems to be a double standard as to what is explicit and what isn't. The most prominent example is the lack of distinction between a Major 7th chord and a dominant 7th chord.

Notice how the two Roman numerals circled in red look like they might represent the same quality: Diatonic seventh chord qualities in C major

  • Both Roman numerals are capitalized
  • The figured bass suggests the same inversion

However, they are both representing different qualities. There is no quality symbol suffix (Δ, Maj, or Dom) to disambiguate them. This is especially confusing, because this syntax clashes with the syntax of jazz/pop chord analysis. "X" (the alphabetic root of the chord) immediately followed by 7 signifies a dominant chord quality in jazz/pop chord analysis (see the chord symbol underlined in yellow).

Additionally, using the syntax above, you'd have to contextually think about the scale degree of the chord in order to inference the quality of 7th chord you are dealing with, which presents added hurdles for both beginners and modern learners versed in jazz/pop syntax.

Why not explicitly include quality symbol suffixes for seventh chords (such as -, Δ, Maj, Dom, etc.) like in the manner below?

Diatonic seventh chords with alternative labeling proposed

Common practice composers didn't consider dominant seventh chords to be stable entities, which is a large reason for the lack of disambiguation. In music of that era, V7/IV is a more functionally appropriate way to describe a dominant 7th chord built on the first scale degree. But in the modern age, in the music of Gershwin, Ravel, or jazz and blues in general, the I7 can function as an entirely stable entity, devoid of any secondary function at all. Hence, I think Roman Numeral analysis should take some cues from jazz chord analysis and become a bit more explicit.

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Short Answer

The two systems are intended to describe different things: Roman numerals are interpretive (and designed to describe common-practice period major/minor tonality); chord notation is intended to be practice, and doesn't necessarily reflect the harmonic role of the chord.

Addition explanation

The Roman numeral system is intended to give the contextual role of the chord. So it's a given, when one is sufficiently familiar with the system, that I7 is a major seventh chord, V7 is a dominant seventh chord, and ii7 is a minor seventh chord (in a major key). A I chord with a minor seventh would not be labeled as a I chord; most likely it would be V7 relative to the fourth degree of the scale (that is, in the key of C, a Ib7 chord would actually be V7 of F).

The jazz/pop chord notation is intended to be practical, thus the qualities of seventh chords are made explicit in the notation. "Even worse" jazz and pop don't necessarily follow the roles assigned to various Roman numerals. For example, the I chord is a blues is typically a dominant seventh chord. This runs counter to the system of major/minor tonality that Roman numeral analysis is intended to describe.

Conclusion

The ambiguity described is relative. Chord notation is highly ambiguous if one wants to look at harmonic interpretation; Roman numerals are "ambiguous" in the way described if the goal is practical realization of the harmony.

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  • Thanks for the explanation. On account of the fact that the I7 in the common practice functions as a secondary dominant, it makes sense that there is no symbol reserved for it. But obviously, a I7 chord in the music of Gershwin is a perfectly stable entity. I guess the symbols detail the usages found in the common practice era, which are slightly outdated. Another thing to ponder is why anyone would go so to far to capitalize anything if everything is contextual? Is there a strong need to symbolically disambiguate the capital I from the lowercase ii if the context is known to be major? Feb 27, 2021 at 22:51
  • I think more explicitness might be a good thing to adopt into the system going forward. Just as we want to disambiguate the IV from the iv in modal mixture scenarios in the music of Bach, we'd probably want to disambiguate the I7 from the IMaj7 in the music of Gershwin. Feb 27, 2021 at 22:54
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    @NakulTiruviluamala It depends on one's intention. IMaj7 is considered consonant in the music of Gershwin, but dissonant in the music of Bach, Mozart, or Beethoven, for whose music the Roman numeral system was devised. It's the same core issue as I7 being a tonic chord in blues but not in classical music.
    – Aaron
    Feb 27, 2021 at 22:58
  • @NakulTiruviluamala a secondary dominant seventh built on the tonic should typically be analyzed as V7/IV, not I7, which indicates (among other things) that the seventh is lowered. True major seventh chords are very rare in common-practice style; major sevenths are far more commonly seen as a 7-6 suspension. I know of one IV7 in Handel. Because seventh chords are unstable, anything that looks like I7 is probably in actuality IV7/V or some other secondary harmony.
    – phoog
    May 2, 2023 at 8:53
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Extensions are based on figured bass, and therefore relate to the diatonic scale. V7 isn't a major minor-seventh just because that's the most common seventh chord, it's a major minor-seventh because if you climb the major scale in thirds from the fifth degree, that's the chord you get; in contrast to I7, which, containing the seventh scale degree, is a major seventh. We don't tend to adopt jazz-like notation (e.g., I♭7), even though modified intervals exist in figured bass, for much the same reason we tend to refer to III as V/vi -- we're not just talking about chords when we use roman numerals, we're talking about chords in relation to other chords.

We use upper/lowercase (alongside modifiers for diminished and augmented) because altering specific scale degrees/borrowing chords from the parallel key is extremely common and needs to be accounted for. I guess you could view minor-key V as being shorthand for V/I if you really wanted, though it puts you in the weird position of recursively viewing minor-key I (as in, a Picardy third) as I/I, and doesn't accurately convey the fact that V is just an ordinary part of minor tonality with a distinct function from v.

This system is a little limited (though less limited than you seem to think), but it exists primarily to describe music which broadly conforms to these limitations.

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    The weakness AND the strength of the roman numeral system is the need to define where the functional key changes take place. This will decide both numbers and quality. For instance, when a tune in c major uses em7b5, it implies a key change to F major, since the m7b5 chord can only take place on the seventh step. The alternative to indicate a change to F major is to mark the chord iiiø... May 8, 2023 at 13:56
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Consider that RN basically has any note in a chord - especially four-note chords - as a diatonic note. So 'stacking thirds' will automatically result in I7 being a major 7th, and V7 a dominant.

To differentiate, 'I dominant seventh' will be labelled V7/IV - the dominant seventh of the four chord - or a C7 dominant chord of F. That way, there's no confusion.

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  • Why does roman numeral analysis use capitalization to disambiguate Major from minor if everything is purely based on inference? I'm pointing out that there seems to be a double standard as to what is explicit and what isn't. In the common practice, it is indeed correct that the I7 functions as the V7/IV. But in the modern age, in the music of Gershwin, Ravel, or jazz&blues in general, the I7 can also be an entirely stable entity on its own accord, and not serve a secondary function at all. Hence, I think RNA should take some cues from jazz chord analysis and become a bit more explicit. Mar 1, 2021 at 6:26
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What are you trying to analyze? Use an analysis method that matches the harmonic style of the piece you're analyzing.

Roman numeral analysis was developed to analyze diatonic functional harmony in the major/minor key system.

In Roman numeral analysis the Roman numeral designates the chord root.

The Arabic numeral figures indicate the intervals above the bass (not necessarily the chord root.) Certain figures are often assumed and not listed. For example 7 implies intervals 7 5 3, or 6/5 implies 6 5 3.

The specific qualities or chords and intervals are determined by the diatonic key signature.

So, symbols like I7 and V7 are understood to mean diatonic seventh chords rooted on the tonic and dominant in root position. As diatonic chords that means the diatonic seventh chord rooted on the tonic is a major seventh chord and the one rooted on the dominant is a dominant seventh chord.

Some, but not all Roman numeral analysis, uses letter case to indicate is a chord third is major or minor, upper case for major thirds and lower case for minor thirds. Additionally symbols like o, ø, +, etc. may be added for qualities like diminished (triad), half-diminished (seventh chord), or augmented (triad).

Older examples of Roman numeral analysis tend to use us upper case Roman numerals and more modern systems tend to use letter case and lots of marking for chord quality.

You need to know what system is being used. II7 and ii7 could mean the same thing: a minor seventh chord rooted on the supertonic, depending on the system being used.

Roman numeral analysis was developed before jazz. It is not meant to be a lead sheet tool like jazz chord symbols. If you are looking for the "classical" equivalent of a lead sheet, the more appropriate thing to look at is figured bass.

It helps to understand the historical context behind Roman numeral analysis and the harmony style it was meant to analyze. You really need to go back to Rameau and the advent of chord root theory. When harmonic thinking shifted to chord roots, part of the revelation was understanding much of harmony was roots by descending fifths even if the bass and other voice movements were not moving by fifths. Labeling the chord roots with Roman numerals then becomes a convenient way to clarify such root progressions. Chord roots were the first concern.

Harmonic style at that time was more prescribed that later times - especially when you compare it to Ravel, jazz, etc. - and a lot of detail could be assumed in the Roman numeral analysis. For example, if a harmonic passage in a minor key was labeled II V I, using older Roman numeral analysis, the assumption would be diminished supertonic chord, major triad of the dominant, minor triad of the tonic. Such assumptions could be made, because at that time playing in a key followed certain conventions. The analysis just followed suit with those conventions.

I think Roman Numeral analysis should take some cues from jazz chord analysis and become a bit more explicit.

Some harmony textbook authors have. But there isn't one universal system. It depends on what their texts are trying to cover. You need to understand what those authors are trying to illuminate, especially if they are trying to cover both the common practice era, which was concerned with diatonic major/minor keys, along with modern style using impressionistic, modal, or jazz harmony.

I have Kostka/Payne's Harmony, which uses plain 7 for dominant seventh chord, and labels like Maj and Dom in places, like IMaj7, for clarity. Their text also includes analysis of a very chromatic passage by Chopin and the analysis is done with both Roman numeral and alternative analysis. The chromatic passage is labeled with letters and qualities like A♭Dom7 D♭M7, but also uses an ellipse to represent the long, non-functional passage as I ... iiø7 V7 I. I particularly like that use of an ellipse, because it keeps the focus on function in diatonic major/minor keys.

Personally, when I have tried analyzing music after the common practice era, something like Debussy, I have used a combination of methods that seem to match the musical passages. In Debussy there are sometimes V I type progressions, and when the musical thought behind the music seems to be cadential harmony, I label it with Roman numerals. Other passages may be more chromatic, so I might use jazz chord symbols. In such passages I look out for sequential designs and label them, or I might just label the interval progressions of roots (or the bass.) If a passage is "exotic", modal, I might just label the scale or mode.

Analyze with methods that describe the thinking and design behind the music.

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