What chord is "A7+4"?

Question

That's how it's notated and I think it's a really unusual notation. Could that be a synonymous notation for "A7sus4"?

The key signature is E-flat.

Answer 1

^{This answer assumes that 7#11 chords are equivalent to 7b5 chords, and it uses the two symbols interchangeably. I acknowledge that there are in fact some pedantic differences between the two, but for the purposes of this answer, those differences are unimportant.}

^{I am also working under the assumption that the perfect fifth of the chord is always going to be omitted from a 7#11 chord, thus the only possible contrast between 7#11 and 7b5 arises from the spelling of one of the notes. I do not think it wise to delineate the two here. In the same spirit, the tritone sub for Eb7 would be "more correct" spelled as Bbb7 rather than A7, but that is a topic for another day and I'm not willing to die on that hill either - I'm picking my battles!}

This question was updated to include context. The section below is my original opinion on what the chord symbol "A7+4" could mean in isolation:

What does A7+4 mean (by itself)?

This is a really unusual chord symbol, so the interpretations are not going to be easy. In my view, it is likely that one of three possibilities was intended. I have italicized strategically to show what effect the "+4" part of the symbol has on the chord in each example:

A7+4

1. A augmented dominant seventh chord with an added fourth
2. A dominant seventh chord with an added augmented fourth
3. A dominant seventh chord with an added fourth

What are the points for and against these interpretations?

1: The "+" symbol should normally mean "augmented fifth", so the symbol A+7 (sometimes A7+) indicates an augmented seventh chord. The first possibility on the list uses that standard logic, and then interprets the "4" separately as an added note.

This is probably the most standard and literally correct method of parsing this notation, but this particular chord symbol is very rare and there are some arguments for other interpretations. If this is the right way to read the symbol, the chord should be [A C# D Ex G]. Unusual to have the perfect fourth rub against the major third, and especially with an augmented 5th, but not technically impossible. Seems like the kind of chord one gets by vainly trying to include a bunch of non-chord-tones and suspensions into the chord symbol.

2: The "+" symbol can also be read to only mean "augmented", which normally gets attached to the fifth by default. With this reading, the added fourth takes the augmented quality since the "+" precedes the "4", and the resultant sonority is [A C# D# E G]. The augmented 4th (or diminished fifth) is a very common extension on the dominant chord in jazz music (which happens to be a genre where weird chord symbols are common), and almost certainly a jazz musician would take the liberty of omitting the perfect fifth.

The resulting altered dominant voicing is very common, and this sonority also takes the form of the French augmented sixth chord (Fr+6) in classical analysis. However, A7+4 is not a good symbol to represent this voicing if this was the desired chord. For jazz, something like A7(#11) or A7(b5) would be best - parentheses optional.

3: Here, the "+" symbol is used erroneously in place of "add" notation, simply asking the player to add the fourth to the dominant seventh chord. The resulting chord would be played [A C# D E G].

While a theoretically valid (if a bit uncommon) chord in its own right, this would be a notation mistake. It is unadvisable to use a "+" symbol to mean "add", since it is already in standard use for augmented fifths. If "add" was desired, there are many better alternatives such as A7add4, A7add11, A7(4), A7(11), or even A7/11. It is not uncommon for beginners to assume the "+" means "add" (read: check your author's credibility!), and in context it might work for some familiar audiences, but this is generally not accepted as far as chord symbol conventions go.

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In-depth analysis using the context of the song:

With the new information (this chord lands on "bow" in the song "Somewhere over the Rainbow" in the key of Eb), it is possible to deduce much more about the intended chord:

Knowing that the chord progression is more like Eb % % % G-7 % E-7 "A7+4" Abmaj7 [...], the chord is undoubtedly supposed to be the altered dominant chord A7#11 (or Bbb7#11, possibly). This is what I described in example #2 previously. Since this answer is getting quite long-winded, I'll repeat that: to play this song, play this as A7#11, or [A C# D# G].

How can we be so sure?

First, let's examine the surrounding harmony. Recognizing the fact that E-7 and A7 make a ii-V in the key of D major, which is a tritone away from the target chord Ab in the next measure, is crucial. Thus, our progression is something like:

I % % % |
iii-7 % sub(ii/IV) sub(V/IV) | IV ...

These are tritone substitutions for secondary dominants. They look confusing in RNA symbols, but all that's happening is the arranger is making a nice "ii-V-I" progression aimed at the IV chord, then replacing the ii and the V with chords rooted a tritone away. This is pretty standard jazz harmony. The voice leading is smooth and chromatic while also maintaining functional harmony patterns.

The idea that this mystery A chord should be A7#11 makes a lot of sense. In fact, 7#11 chords are symmetrical at the tritone, so this will have the same notes as an Eb7#11 chord. An Eb7 chord would be the normal dominant that points to our target Ab - that's what we substituted for in the first place! Additionally, the melody note Eb is actually a chord tone of an A7#11 chord (enharmonically speaking), which is a fact that gives this theory a lot of weight. This A7#11 is so logical that it renders the other interpretations unthinkable - neither one includes the melody note, nor do they make much sense in this (or any) context.

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Questioning the effectiveness of this chord symbol:

Does the "+" have to mean "augmented fifth"?

I think it's safe to say that we've sorted out what the symbol was supposed to mean in the music. But was it a good chord symbol to use for that desired sound? I argue that this was a poor decision by either the editor or whomever is responsible for writing up the chord labels. In my experience, the "+" symbol is solely used to describe an augmented 5th. By contrast, when the sharp eleventh or fourth is desired, it is represented as "#11" or "#4".

Almost all chord tones take their modifications via accidentals in the chord symbol; for example, when the ninth of a dominant chord is lowered, its chord symbol is 7b9. The eleventh, in my experience, follows this rule like all of the other extensions do. The only exceptions are:

• The root, which it goes without saying will never change,
• 3, whose information is deduced from the symbol for the seventh,
• 5, which can be changed with "+", "°", "ø", or with accidentals like the rest of the extensions,
• 7, which is changed with "maj", "m", "-", "-(maj)", "", et cetera.

There is such thing as an augmented 6th chord, and it actually does use the + symbol for the raised sixth, but that is archaic usage that dates back to the figured bass tradition and I have yet to experience musicians use the + sign for "sharp" in modern chord-labelling contexts. In any case, the 11th cannot be changed by the "+", and the lack of contradictory instructions is strong evidence that "+" should apply to the 5th since the base chord type should be "+7". After all, what would "C+maj7" mean if the "+" could be applied to either the 5th or the 7th? Only when applying the standard nomenclature does it become clear that the 5th is augmented and the 7th and 3rd are major.

How should the piece be played?

According to standard chord nomenclature, the use of the "+" symbol indicates unambiguously that the 5th of the chord is to be raised by a half-step. For that reason alone, #1 in my original post should theoretically be the "correct" way to play that chord symbol. However, context indicates that this was obviously a mistake in the notation rather than an intentional call for a ridiculous chord. "Theoretically correct" does not mean anyone would actually do this, nor does it mean you should try to play it that way. But it is still bad practice to write like this because it makes the music unnecessarily hard to read. I can't think of a single reason not to call this chord one of the universally agreed-upon labels: 7#11 or 7b5.

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Further Reading / References:

• The Wikipedia article on altered chords never acknowledges the use of "+" for sharpened intervals other than the 5th.
• Hello Music Theory has an altered section of their chord naming info page that prescribes only accidentals for alterations.
• Music Novatory actually does prescribe the use of "+" in their chord symbols page; however, this is for something they put in a section called "Chromaticism" and it appears that they use these for every single interval above the root. The website also prescribes some strange non-traditional analysis tools like motrixes, proper tones, and common tones. Go ahead and read up on this, since I just gave it a glance, but I would consider this kind of theory to be outside of the domain of standard jazz chord nomenclature.
• Dobrian's list of jazz chord symbols looks to be a fairly large collection of chord symbols for jazz music. However, the "+" symbol only appears for the augmented triads and augmented 7th chords.
• jazz-library.com has an article listing chord symbols; as before, the "+" character only appears in the augmented triads and augmented seventh chords. Certainly no "+" symbols for augmented 4th alterations.
• guitarcommand.com has an [article on altered chord theory], and the "+" character stays within its scope as the augmented 5th quality marker.
• I like to include some native SE content in my research; this Music: Practice and Theory answer does mention use of +/- as an alternative to #/b when altering chord tones. Unfortunately, no references have been provided for this, and the example given is for a sharpened 9th rather than a sharpened 4th, although I will concede that it is very likely that the fourth would follow the same pattern as the ninth given that it is enharmonic to the eleventh.
• Another of M:P&T's very own posts caught my attention by using the symbol "+6(b9 #9 #11)". Sadly, this can only mean [1 3 #5 6 b9 #9 #11], as this symbol was being used to describe the chord built on the leading tone of the harmonic minor scale.

Answer 2

The + here means #: that is, A7#4. In fact, were it really accurate, it would be A7b5. The Eb in the melody is the b5 relative to the A chord (#4 being D#). It's understood in this case that the #4 replaces the normal fifth of the chord (E).

The E-7 moving to A7b5 is a sort of tritone substitution for a ii-V progression (Bb-7 Eb7) leading to the AbMaj7 that follows.

Here'a possible voicing. Notice how the notes in the chords descend.

Notes in parenthesis are not part of the descending pattern

Top notes:     (D)  D  C#   C
"Alto" notes: (Bb)  B  A    Ab
"Tenor" notes:  G   -  -    -  (stabilizing pitch)
Bottom notes:   F   E  Eb  (Eb)

Answer 3

Tldr; You probably shouldn't be adding a 9th or 13th (or even potentially a 5th) to this chord^{insert 10 caveats}, which is why it's written as A7♯4 instead of A7♭5 or A7♯11. The + means ♯, and this is A7♯4.

An important PSA: in jazz, a well-written chord symbol does more than simply spell out the notes. It provides information about the underlying harmonies, which is especially important because the notes A-C♯-E♭/D♯-G could convey many different harmonies (altered, Lydian dominant, half-whole diminished, whole tone, etc.). The band needs to be on the same page when they see an altered chord in a lead sheet. That's why we can't conflate harmonically equivalent spellings.

There's really only one answer: Given all of this, @Aaron is absolutely correct that A7+4 means A7♯4. The + is the same as # here.

How to interpret other answers: Other answers make some attempts to determine whether this particular instance of A7♯4 is equivalent to A7♯11 or equivalent to A7♭5, but that depends entirely on context and won't be true in all cases. Some answers argue that A7♯4 is always the same as A7♯11 or A7♭5, and I disagree with those answers.

Here are the main differences, in general [insert 10 more caveats about how rules are meant to be broken]:

• A7♯11: This implies harmonies with a natural 9 and natural 5 (like Lydian dominant).
• A7♭5: This is very different from A7♯11 because it implies harmonies with a b5 and often implies alterations on higher extensions too (♭9, ♯9, ♭13). Examples include the altered scale and whole tone scale.
• A7♯4: This is more flexible and a little ambiguous. Often it's equivalent to A7♯11, but sometimes it implies whole tone (as in A7♯4♯5) or half-whole diminished. Other times (and this is the correct interpretation here, I think), it's the best way to convey "play the note between D and E and don't add upper extensions like the 9th or 13th." For example, you'll notice that Aaron's example of how to voice this chord doesn't include a natural or sharped 5, doesn't include a 9th, and doesn't include a 13th.

How to figure out the answer: Go to the piano and play the 3 measures in question ("somewhere over the rainbow") 3 times. On each pass, try a different voicing (shown below) for A7♯4. In all 3 passes, play Emin as E-G-D in the RH and just E in the LH.

1. voice A7♯4 with a B Maj upper structure triad (2nd inversion) in the RH and A-C♯-G in the LH
2. voice A7♯4 with an Eb Maj upper structure triad (1st inversion) in the RH and A-C♯-G in the LH
3. voice A7♯4 with C♯-G-D♯ in the RH and A-G in the left hand

Similarly, trying adding a 5th to the A7#4 chord. Which sounds best?

1. adding the ♮5 (e.g., E-A-C♯-D♯ in the RH)
2. adding the ♯5 (e.g., F-G-C♯-D♯ in the RH)
3. adding neither (e.g., C♯-G-D♯ in RH)

Really, they all sound good, and it's a subjective judgment call. However, some are more exotic than others, and given that A7♯11 isn't explicitly written, playing a B Maj upper structure triad may clash with what the rest of the band is doing. Because of the ambiguity about the 5th, 9th, and 13th, I think this notation of A7♯4 is supposed to convey a simpler voicing in this particular case.

Caveats: If someone were improvising over this, it would be silly to simply avoid playing the 9th and 13th. So, they will usually have some flexibility to decide which scale/harmony they want to use. The band would generally follow along, unless a band leader specifically said something like "treat that as whole tone."

Answer 4

The other answers are so long!

For brevity's sake:

A7+4 would mean "A dominant seven, augmented fourth" which is an enharmonic spelling of A7♭5 "A dominant seven, flat five", an augmented fourth being enharmonically equivalent to a diminished or "flat" fifth.

Given the E♭ in the notated melody, I would think A7♭5 would be the more appropriate name.

Also, if you use smooth, step-wise voice leading, the tones descend from E natural in Em to E♭ in A♭Δ. Spelling the in between A7+4 chord so that the line is E♮ D♯ E♭ seems an awkward way to show a descent with a repeated tone. Overall, the harmony of the opening is a move from I to IV where E♭ the tonic is common to both chords. Actually, it's a tonal degree whether I or IV is tonicized. It seems odd to enharmonically respell a tonal degree as D♯ when the harmony is just chromatic decoration.

Answer 5

There won't be a ♯4 or a ♭5! True, + means ♯.

Funnily enough, Big band has just re-started after 18 months, and this piece is one of the first we looked at.

Albeit in a different key (B♭), that bar is Dm7 - Bm7 E9(♯11). Transposing to Gm7 - Em7 A7+4. That A7+4 should be, according to my chart, A9(+11).Or A9(♯11). It produces a chromatic dropping of the lower notes in the chords for the preceding and next bar (not shown on my pno copy, but heard from bass and trombones).

It's not usual to have ♯4, but ♯11 is commonplace. Rather like ♯2 or ♭2 isn't seen, whereas ♯9 and ♭9 are. That puts the altered note an octave away from a note it would clash with.

In my chart, being 9(+11) means there would be 1,3,5,♭7,9, and the ♯11 available to be played by many different instruments.