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Thread: Seventh chords as Roman numerals

  1. #1
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    Seventh chords as Roman numerals

    I'm looking at the 7th chord written on the first degree of the major scale. Seems to me that, as a Roman numeral, it's I7. Or, is it Imaj7? Or does it depend on the chording system used?

    Thanks,

  2. #2
    Registered User JonR's Avatar
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    Quote Originally Posted by ceilr View Post
    I'm looking at the 7th chord written on the first degree of the major scale. Seems to me that, as a Roman numeral, it's I7. Or, is it Imaj7? Or does it depend on the chording system used?

    Thanks,
    Depends on the system.
    Classically, it would be I7, because you're just adding the diatonic 7th. But pop, rock or jazz readers would (IMO) expect to see "maj7".

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    If I saw a chord written as I7, I would think the writer meant a dominant seven chord (ie major chord with the 7th made flat).

    Unfortunately in music you do find all sorts of different conventions being used for the same thing. Symbols such as triangles and small circles etc., used for dominant, diminished and half-diminished chords. Also the use of a minus sign to denote minor chords. Lack of consistency over using upper case and lower case Roman numerals to denote different chord degrees.

    I guess itís just a matter of getting used to all those things as a result of working from different books which use the different conventions. Eg, Iíve been working a lot from Garrison Fewellís book on improvising jazz with "upper structure triad extensions", where he uses a minus sign for minor chords, so Iím used to seeing that now.

    It seems to meet that you meet more of those different conventions in jazz books of that sort Ö otherwise you may never meet them, or when you do it will seem confusingly unfamiliar.

  4. #4
    Registered User JonR's Avatar
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    Here's some links to various explanations. Most go with the classical system (as any bona fide theory site should, at least as a starting point).

    http://musictheoryblog.blogspot.co.u...-notation.html
    http://www.musictheory.net/lessons/49
    http://www.8notes.com/school/theory/...l_analysis.asp
    http://en.wikipedia.org/wiki/Chord_(...Roman_numerals
    (wiki mentions a few systems, but doesn't go into detail)

    You get other complications with figured bass, where the arabic numbers (6, 7 etc) refer to inversions, not chord extensions. (The numbers still mean intervals, but from the bass note in the specific inversion, not the chord root.)
    http://musictheoryresources.com/members/FA_rom_num1.htm


    Chord symbols as used in song charts in pop, rock and jazz have a different purpose of course: to enable readers to play the chords . In real music, chromatic chords, modulations and non-functional chords are so common that any chord symbol system needs to specify the chord type clearly, not refer it to a key context, which would take too long (and require too much theory knowledge!) for a player to work out when sight-reading. (And of course there may be no key context at all...)

    IOW, in classical harmony, chord symbols are for analysis, and one would begin from notation (bass and figured bass at least), and a reasonable idea of the local key. They are therefore dependent on key. Chord symbols in jazz/rock/pop charts are independent of key (you can work out the notes in a chord just from its symbol, without needing to look at the context).
    Last edited by JonR; 05-16-2012 at 10:41 AM.

  5. #5
    Registered User ernzzz's Avatar
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    Also there's a "mistake" in chord nomenclature itself when regarding to 7ths..

    A7: has the b7
    A maj7: has the 7

    Am7: has the b7
    AminMaj7: has the 7


    If we named the chords by the real 7th they hold..

    A7 should mean Amaj7, while A(b7) will be the old A7..

    Am7 should mean AminMaj7, while Am(b7) will be the old Am7

    and so on..

    I guess it makes it easier and faster for refeering to dom7th chords, but nonetheles it is there..
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  6. #6
    Registered User JonR's Avatar
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    Quote Originally Posted by ernzzz View Post
    Also there's a "mistake" in chord nomenclature itself when regarding to 7ths..

    A7: has the b7
    A maj7: has the 7

    Am7: has the b7
    AminMaj7: has the 7


    If we named the chords by the real 7th they hold..

    A7 should mean Amaj7, while A(b7) will be the old A7..

    Am7 should mean AminMaj7, while Am(b7) will be the old Am7

    and so on..

    I guess it makes it easier and faster for refeering to dom7th chords, but nonetheles it is there..
    Yes -again, you're referring to chord symbols in charts, for playing from. Not to the principles of roman numerals for analysis.

    The principle that our "playing" symbols follow, btw, is to keep the shortest chord names for the most common chord types. (As with all notation for reading, the governing principles are economy, speed and clarity.)

    So "m" always refers to the chord's 3rd, while "maj" refers to its 7th. In the absence of either, we have a major 3rd, and a minor 7th (b7) - the dom7 being the most common 7th chord type.
    The rarest is the minor chord with the major 7th, so that can have the longest name.

    The "real 7th" is not a very useful concept, IMO. I know you mean the diatonic 7th, but the I, IV and V chords in a major key have different diatonic 7ths anyway. I and IV have a major 7th naturally, and V has a minor 7th naturally. So both are "real".
    IOW, for an A chord to have a major 7th as its "real" (natural) 7th, it would need to be I in A major or IV in E major. If it was V in D major, then a b7 is normal.

    As an extension, the minor 7th is more common than the major 7th anyway. A major scale features 5 minor 7ths and only 2 major 7ths. So (even if dom7 chords weren't so common), it makes sense for the minor 7th extension to be labelled plain "7", with the rare major 7th labelled "maj7".


    But when it comes to symbols for analysis, then "7" does mean whatever the appropriate diatonic 7th is, for the context. So "I7" in the key of A major would mean what you and I would call "Amaj7"; "IV7" would mean Dmaj7; "V7 would mean E7; "II7" would mean Bm7; etc.
    Last edited by JonR; 05-16-2012 at 12:15 PM.

  7. #7
    Registered User ernzzz's Avatar
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    Quote Originally Posted by JonR View Post
    The "real 7th" is not a very useful concept, IMO. I know you mean the diatonic 7ths anyway....
    Well not really diatonic to a key, i meant just interval construction from a given root, no functional harmony implyed...

    The numeration of intervals is also based on the major scale, but thats another story..


    Quote Originally Posted by JonR View Post
    But when it comes to symbols for analysis, then "7" does mean whatever the appropriate diatonic 7th is, for the context. So "I7" in the key of A major would mean what you and I would call "Amaj7"; "IV7" would mean Dmaj7; "V7 would mean E7; "II7" would mean Bm7; etc.
    Right.. never thought about it, but is very important to understand the distinction of things that refeer to a diatonic context, or just an intervallic construction
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  8. #8
    Registered User JonR's Avatar
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    Quote Originally Posted by ernzzz View Post
    Well not really diatonic to a key, i meant just interval construction from a given root, no functional harmony implyed...

    The numeration of intervals is also based on the major scale, but thats another story..
    Well, yes and no. Or rather, no and yes

    If the numeration of intervals was based on the major scale, then "A7" really would mean Amaj7. But it doesn't. Therefore it's not based on the major scale. (The idea that it is is an assumption after the fact, which kind of works up to a point.)

    It would make more sense - it would describe the numbering convention more accurately - to say it's all based on mixolydian mode!
    But of course it's not that either.

    In fact, chord symbols are not derived from any particular scale, but are a shorthand that's evolved from practical usage by musicians, generally in popular music and jazz; not from any preceding theoretical plan. The first and main chord to get a 7th added would have been the V chord. So, a plain number "7" would have been the simplest indication of that. (A "b" would have been unnecessary, because it was just the normal diatonic 7th.)

    It was later that it was realised that it was important to distinguish the major 7th interval, hence "maj7" (and triangle, etc).
    It would have been important, as I mentioned, that the symbol language was independent of any scale, so you didn't have to understand the context in order to understand the symbol. So the symbols had to incorporate a way of distinguishing between chord types.

    The demarcation of "m" for the minor 3rd and "maj7" for the major 7th meant that chord symbols could be very economical.
    After all, if one was going to spell out chords in full (to be as clear as possible), they'd need to be something like:
    Amaj/maj7 (A C# E G#)
    Amaj/min7 (A C# E G)
    Amin/min7 (A C E G)
    Amin/maj7 (A C E G#)
    (perfect 5th assumed in all cases of course)

    - a bunch of confusing mouthfuls there!

    But if we establish that a major 3rd and minor 7th are standard - so don't need to be mentioned in the symbol - and only deviations from the standard are indicated, that makes it simple:
    A...maj7 (A C# E G#) - standard 3rd, raised 7th
    A...7 (A C# E G) - standard 3rd and 7th
    Amin...7 (A C E G) - lowered 3rd, standard 7th
    Amin...(maj7) (A C E G#) - lowered 3rd, raised 7th

    When it comes to diminished chords, the altered 5th comes into play. The symbol has to indicate that. So the plain triad is called "dim". (The minor 3rd being assumed.)
    As with major and minor chords, dim triads can have two kinds of 7ths added. But in the case of dim triads, instead of major and minor 7ths, the 7ths are minor or diminished.
    So in full the chords would be described as:
    Adim, min7 (A C Eb G)
    Adim, dim7 (A C Eb Gb)
    The problem here - if we employ the previous system of a plain figure "7" for the minor 7th - is the first chord would be called "Adim7". So what then do we call the second one?

    So the system is adapted. The second chord is called "Adim7" - suggesting that "dim7" refers to the distinctive A-Gb "diminished 7th" interval. It can also be called "A full diminished".
    The first chord can also have two names. It can be called "Am7b5" - suggesting it's an altered m7 chord (which on the face of it it could be); or it can be called "A half-diminished" - because it only has one diminished interval (b5), in comparison with the two in Adim7 (b5, bb7).

    I freely admit here that I'm constructing this system with hindsight, after the event . I don't know if any such thinking went into the process of naming these chords - probably not. But it does make sense this way, as a mix of practical consideration - common practice and economy of reading - and superficial logic. The logic has exceptions of course, as befits an ad hoc system that's evolved piecemeal over decades: "whatever works". It does all hang together, even it's a little shaky at the edges.

  9. #9
    Registered User Color of Music's Avatar
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    Here's where an understand of intervals comes into play. Many of us, were taught to count from the root up in half-steps; however, it's much faster to count down (as with finding the relative minor key. C - three half-steps = a)

    Regarding sevenths:

    Minor sevenths (ie: C7; it's a dominant seventh, but that's something else)

    They're a whole step below the tonic (5 tones upwards) Bb-C-E-G (C-E-G-Bb)

    Major sevenths (ie: CMaj7)

    They are a half-step below the tonic (5 and a half tone upwards) B-C-E-G (C-E-G-B)

    Minor-minor 7ths: (ie: Cm7) The first minor is referring to the third being lowered; this doesn't affect the seventh.

    Minor-Major sevenths: (ie: CmMaj7) Same thing

    The whole idea behind the naming is to teach you the intervallic relationship in the chords; we just don't use them because it understood that we uderstand what they mean.

    That another thing, it's okay to think backwards when dealing with music. Much like math - not all problems can nor should be solved working forwards.

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