I'm learning jazz and playing from lead sheets and am confused about how to handle triads that do not explicitly say what to do with the 7th. If the lead sheet I'm playing from just describes a chord as G, what are my guide tones for that? If I decide to just throw in a minor or major 7th, am I changing the function of the chord?
A plain triad sounds a lot different and either a major or a dominant chord, so I've been almost thinking of them as their own kind of chord.
Direct answers
Guide tones:
Major and minor triads generally are not thought of as having guide tones in the way seventh chords are, since they are considered stable within themselves; whereas seventh chords are considered inherently unstable and needing to resolve. The guide tones are the notes that most typically are the primary points of resolution: the third and the seventh.
To the degree there is (contextual) tension in a major or minor triad, the third of the chord is the first place to look, as it will often be the leading tone of the following chord.
Does adding a seventh change the function of a chord?
One should proceed as though it will. Turning a major triad into a dominant seventh, for example, potentially signals a modulation. It might or might now work depending on the musical context. Similarly, turning a dominant V chord into a major seventh weakens its function as a dominant chord.
Triads and seventh chords as separate entities
Music theory considers triads and seventh chords as separate entities. Further extensions (9ths, 11ths, 13ths) are generally interpreted in terms of the underlying seventh chord.
Detail
When a score calls for a triad, it should be played as a triad, without a seventh. Adding the seventh changes the sound and function of chords and risks clashing with the melody.
It is often okay to add a sixth to a triad, for color, because adding a sixth doesn't change the nature of the chord in the way a seventh does.
If the performer judges that a seventh can be played where a triad is specified, then one can follow @Tim's guidelines for major keys and the following for minor keys:
Minor key seventh chords i = m7 (or mM7 if the seventh is raised) iio = 7b5 (half-diminished) III = M7 iv = m7 v = m7 (or V7 if used as a dominant chord / with raised seventh) VI = M7 VII = 7 (i.e., dominant seventh)
Be careful, when adding sevenths, that you're aware of any modulations. For example, if one is in the key of C major, but encounters the triads F and Bb at a cadence point, then the minor seventh would be added to the F chord — creating an F7, the dominant of Bb — rather than the major seventh, which would otherwise be consistent with C major.
A basic, simple 'rule' is that we have Ⅰ, ⅱ, ⅲ, Ⅳ, Ⅴ, ⅵ, ⅶ° as the main triads diatonically.
The 7ths associated with those are as follows: ▵, m7, m7, ▵, dom 7, m7, °7.
When Ⅰ moves directly to Ⅳ, dom7 is appropriate. But above all, use ears. They will tell, in 99% of cases, whether the choice is good or not.
In short: know what the simple written version would sound like if played literally like that, and then do whatever sounds good to you. You must develop your own sense and taste for what sounds good through practicing and trying things. Theory gives you ideas and tools for finding things to try, and to reason about what others play.
We could solve this question either by writing an endlessly long list of logical rules and checklists that even a deaf person could mechanically apply... or we could solve it like it's actually done: with ear and taste.
The only actual rule is: play whatever supports the melody appropriately for the occasion. If it makes you feel better, play it. If it makes your audience feel better, play it. If it makes you or your co-musicians confused, don't play it.
Chord symbols are written (by people) as guidance for accompanists (other people), and together with the lead melody, they describe the lead-sheet writer's view of what the most important idea of the song is, when described in simple, coarse terms. But it's just a starting point - all that can (and should) be jazzed up in various ways. Whatever chord symbol is written, it's just one possible idea, and each chord symbol should be read as meaning a rough umbrella term as a whole family of possible chords. And even then, you can ditch the whole rough idea and play something from a different family of chords, if you think that it suits your own idea better.
Quote from Jazz Piano Book by Mark Levine
The unhappy fact that the chord symbols C, C∆, Cmaj7, CM7, C6, and C69 all mean pretty much the same thing and are often used interchangeably can be discouraging to a beginner. In this book, I’ll use the ∆ symbol for all major chords.
So, in his book, he writes a "maj7" chord symbol, whenever he means any sort of non-dominant major chord. The actual realization of the described idea (IF you decide to follow that idea and not some other one) can even be a simple triad, or it could be a four-note or five-note chord, and it still fits the same general category. But dominant chords are a different family of roles, as you know.
However, lead sheets are not generally written like that - Levine just wants to say with this notation that many types of chords are interchangeable, and when you see any written chord symbol, you should generalize it in your mind to a wider overall chord family, and then play something within that general ballpark. You learn to do that by trying different things and messing with the songs.
Your example lead sheet of My Favorite Things, starts with four consecutive bars of "Em". It certanly cannot mean that you must hold the exact same chord for four bars, that would be boring, wouldn't it? Myself, I would be tempted to play a descending line: Em - Em maj7 - Em7 - Em6 - ... and on the next line, instead of the written Cmaj7, I would do the same over Am: Am - Am maj7 - Am7 - Am6 (depending on the occasion, maybe trying not to sound like Stairway to Heaven). But then there would have to be yet another change on the third line to get a change there... Maybe if the second line has to be a C based chord, I might alternate between Cmaj7 and D/C, to keep some motion going.
what are my guide tones for that?
Your guide tones are from the chord that you imagine. You might see four bars of "Cmaj7" written on the lead sheet, but if you want to play: C - D/C - C - D/C, then over the imagined C your guide tones are from C, and over the imagined D/C your guide tones are from D/C.
If it says G it might truly mean a G triad. Especially if a country or pop tune.
If that doesn’t sound quite right then it probably means GMaj7 or G6.
If neither of those sounds right then you should look at the chords before and after it and figure it out from the context. So if it is followed by C7, chances are it is a Gmin7, or if it is followed by C7b9 it is probably Gmin7b5.
If it is a 12 bar blues then they probably mean G dominant 7.
Unfortunately, this is a stylistic choice.
You get both the complete freedom, and the complete responsibility of playing within the chosen style.
Some arbitrary guidelines:
It depends on what the next chord is.
"Guide tones" is just another way to say "voice leading" and you need to move to another chord to really say what happens moving tone to tone.
The chord third and seventh are the usual tones when talking about "guide tones", so...
Cm you could add a minor seventh to a G major triad to make G7, where, in terms of "guide tones", a seventh resolves to a thirdG Cm, you can use tone G as the guide, the root of G then becomes the fifth of Cm.If I decide to just throw in a minor or major 7th, am I changing the function of the chord?
Depends how you mean "function." If you mean the standard idea of functional harmony, where functions are pre-dominant, dominant, tonic, then "no" adding a seventh won't change the function. In other words d(dim) G Cm and dmin7b5 G7 Cm6 are both functionally pre-dominant to dominant to tonic regardless of extensions or added tones.
But, as with anything, the devil is in the details. With a progression like d(dim) G Cm you could add a minor seventh to the G chord (add an F natural) and handle it as a chord tone with standard resolution to the third of Cm. But, you could also use an F# over the G chord and treat it like a non-chord tone neighbor tone to the chord root G. The first scenario is the obvious way to set up/confirm a dominant to tonic function, but the second scenario using F# certainly doesn't preclude dominant to tonic function.
I think the fourth bar of a standard 12 bar blues provides a good example to consider. For a blues in G the fourth bar will be a G chord. Some lead sheets might give it as plain G, others G7, and many people might read G but play G7, the next bar will be a C chord. You could describe that change as a tonicization of C when preceded by G7, some might even call it modulation (even though that doesn't make sense.) Functionally it's just a move from tonic to subdominant. When it moves back to the tonic you can even call that a tonic prolongation. But, the important point is that the overall harmonic, functional structure of that 12 bar blues isn't going to change just because you added a minor seventh to the tonic chord. The larger harmonic structure is what will determine function, not the minutiae of embellishing tones.
In other words, you can't really say anything definitely about chord function if you give only one base triad an then consider one added or extending tone.
I'm glad you posted a link to a lead sheet...
...it's so much easier to discuss actual music.
In that four bar passage, there is the plain G major triad given.
What is my 7 if a chord does not specify the 7th?
So, essentially you want to know if you should play a minor seventh or a major seventh over that plain G major triad.
In this particular case you could easier play either type of seven. IMO this is a good example of how the chord/scale system fails. Instead of matching a chord to a scale, you really want to understand harmonic function, and why in this case either seventh type will work.
If you play an F#, you will have a major seventh. That will match the key signature, making it a fairly obvious choice. In terms of function you could then say the D7 G C passage is either Em: V7/III III VI or temporarily shift to G as G: V7 I IV. Either functional analysis is fine. The song clearly works around the shifting minor and relative major keys, and you would say the G chord gets tonicized.
But, you could also play an F natural over the G major triad, that would be a minor seventh. In terms of function that would then be Em:V7/iii V7/VI VI. There would be a sequence of two dominant seventh chords, and you would say the C major triad gets tonicized.
After that particular passage the line continues to end on B7 which definitively brings us back to E minor for the key.
The big picture is an "A" section that is in E minor. Whether you use a major or minor seventh on the G major triad, and which chord get tonicized as a result, doesn't matter to the bigger picture of playing something in E minor. The choice of either would be up to you.
Now consider either the C or Am chords in bars 14 and 15. Here the choices of potential sevenths, following conventional harmony, are more circumscribed. C7 might be questionable, because it doesn't resolve like a dominant (you could call the move the Am a "deceptive" progression, but that might be iffy.) With the Am if you used a major seventh, it would be a G#, which is contrary to the G natural of a key of E minor, and so might not work well. It could work as some type of chromatic non-chord tone.
The point is to be able to analyze the big picture of the harmony in a song, understand chord functions, and then use added and extension tones in a way that works with that harmony. You should have an idea of what the choices mean harmonically.
It's the diatonic one.
Unless the song uses simple I, IV, V chords and you want to retain that simplicity, in which case you won't want to emphasise 7ths (except perhaps V7) much at all (but this isn't really a 'jazz' approach).
Unless your jazz is blues-influenced, in which case I, IV and V will all then tend to be be dominant 7th shape chords.
Unless you're playing 'cool' jazz, in which case even V might get a (non-diatonic) maj7 and there will be lots of 9ths too, and a sprinkling of #11ths.
Unless...
And that's jazz!
