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Which notes to choose when arpeggiating a seventh chord (or whatever other chord with more than three notes). This doubt strike me when reading a sheet music where the bass clef has a seventh chord and the root note is not played. Is there a general rule for which notes to choose when I want to arpeggiate a chord?

I have various doubts about how to play a song when only the chords are available. But when trying to read the score of some musics in order to get the patterns to use. I have face this A7 chord of the image that makes me wonder, where is the A note?

enter image description here

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  • Please clarify: How do you know it's a seventh chord if the root is not played? Does it appear elsewhere in the arpeggio? Posting an image from the sheet music that raised the question would be helpful. – Aaron Oct 21 '20 at 12:50
  • The measure that raised the question was added. – Rodolfo Oct 21 '20 at 13:54
  • The (incomplete) A7 is notated with fingering in the lower clef. How does the question of arpeggiating it come in? It's written out in the score. – Michael Curtis Oct 21 '20 at 14:31
  • @MichaelCurtis OP is confused why the chord is named "A7" given there is no A note in the score. The left hand plays C#o. – user1079505 Oct 21 '20 at 14:42
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    Please can you also show the bar before the one you have shown. Context is also important in music. For example the previous bar could have had an A chord and your bar was a continuation of it. – chasly - supports Monica Oct 21 '20 at 22:14
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Arpeggiating isn't an exact science. You could play two notes (or more) during the arpeggio.

Chord-wise, the first to be sacrificed is usually the 5 note - in chord C7, for instance, the G would go Think about it - without C, it's not a C chord. Without 3 (E), it's not major, and without 7 it's not a 7th chord. So the same could apply in arpeggios.

If someone else is playing the root (say, bass) then that could go, so you could play a chord of more notes leaving the root out.

Or, you don't need to play one-note-per-beat, you could still play all 4/5/6 notes by sliipping in a couple in between the beats.

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I think your question might be better worded as...

why did the composer or arranger of this sheet music use an A7 chord label for chord tones E G #C when the purported chord root A is missing?

The simple answer is: in this case the chord is regarded as an incomplete chord.

Strictly speaking you would say the first chord is a C# diminished chord in first inversion. You could label it like C#dim/E with jazz labeling or Dm: viio6/3 with Roman numeral analysis.

Why would someone treat it as an incomplete dominant seventh rather than an leading tone triad? I think two main reasons:

  • Dominant chords V and leading tone chords vii0 are often treated as theoretically parts of a larger dominant harmony. They are sort of equivalent in dominant function.
  • Root progression by descending perfect fifth is regarded as the "strongest" chord movement.

So, while vii06/3 i and V4/3 i are sort of functional equivalent, the labeling of V using an incomplete chord is a bit more straight forward in showing the dominant to tonic progression.

Another way to understand the omission of the root in this progression is through looking at the voice leading. Here are two basic version of the harmony with the A omitted and included and also with the D doubled at the octave...

enter image description here

The essential voice movements are the leading tone moving to the tonic (C# D) and the subdominant moving to the mediant (G F.) The supertonic to tonic (E D) is a bit subordinate. But notice the treatment of the dominant (A.) That tone doesn't move. There is a kind of redundancy that allows for an omission.

Play the two progressions with and without the A and they sound more or less the same, because they are more or less the same from a voice leading perspective.

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  • If one views the fifth of the tonic chord an an "optional" note, it makes sense to treat the root of the dominant seventh likewise, though from a voice-leading perspective, they should generally either both be present or both be omitted. I think your example with the A omitted would be better if the A in the tonic, rather than the high D, were the note marked in parentheses. – supercat Oct 22 '20 at 18:55
  • @supercat, I do follow what you mean about an A in parenthesis. But I put the D in parenthesis because it wasn't in the original sheet music example. There is sort of two implied things happening. I could do both and add some text annotation. – Michael Curtis Oct 22 '20 at 19:30
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Chord symbols are an approximation and simplification of essential harmonic ideas for accompanists, leaving precise details up to players to decide. Whoever wrote the notation, declared that the essential idea is "A7", and playing the notes written on the lower staff is one possible realization of that idea.

Chord symbols are a way to describe the overall story in rough simplified terms. "Boy meets girl, boy learns piano, girl leaves boy." "A7 Dm" That story can be told in infinitely many different ways, when you get to details.

The same thing has been asked more explicitly here What is the relation of guitar chords to actual notes in the measure? What is the relation of chord symbols and written notes. Notes can draw a more detailed picture of the same idea. And actual performances of the notes are even more detailed.

  • Very low detail level: Chord symbols
  • Medium detail level: Notation
  • High detail level: Recording of a performance
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The simple answer is that this isn't actually an A7 chord, it's a first inversion C# diminished chord.

When you go back before functional root-based chordal practice, you had basso-continuo-based practices. One of the most common guidelines for harmonizing bass scales was the rule of the octave, which typically prescribed a 6-chord (first inversion triad) over the second scale degree, both ascending and descending, which results in a diminished chord. I've recently been coming to realize just how common this harmony was in 18th century music.

Gjerdingen's book on Galant Schemata would call this pattern (descending 2 to 1 bass, with a 6 chord over the 2) a Clausula Vera. Depending on the previous bar, it might even be part of a Prinner.

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    Why should it be 1st inversion C#o? Could it more likely be root Eo? – Tim Oct 21 '20 at 16:49
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    @Tim No. Root inversion Edim7 would have a B♭ (the diminished 5th) as well as a D♭, not a C♯. Furthermore, an Edim chord would want to resolve up a half step to an F chord. Historically, though, 6-chords on the second scale degree (i.e. first inversion diminished triads, in modern terminology) were relatively common occurances, while root position diminished chords were extremely uncommon. – Caleb Hines Oct 21 '20 at 17:22
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The picture in the OP has the appearance of coming from an "easy piano" arrangement. In such arrangements, it is not uncommon for the chord notation and staff notation to differ slightly.

In the case pictured, the arranger is likely trying to preserve both the voice-leading (as discussed by Michael Curtis) and simplicity of fingering/hand-movement. Thus, the "correct" chord is A7, but the arranger felt it would be easier for a pianist playing from the staff notation if an incomplete chord was used.

Since the G is prominent in the melody, it would be fair to replace one or both Gs in the accompaniment with As, giving you a complete chord. I would suggest perhaps leaving the first G as is, to emphasize the dissonance of the harmony, but change the second G to an A to capture the overall flavor of the A7 chord.

It does beg the question why the arranger didn't write the left-hand arpeggio as E-A-C#-A, since the melody carries the G.

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    To answer your question in the last paragraph, from my viewpoint as a composer, using (E,G,C♯) emphasizes the 'minor' or 'incomplete' flavour of the harmony at that point, whereas using (E,A,C♯) would give a more 'complete' feeling at that point. For this reason, it is common to see the A missing from an A7 chord, in a minor piece, but (at least in classical music) it will not typically be missing in a final V7-I cadence. – user21820 Oct 22 '20 at 15:13
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    @Aaron I thought the same about the doubled G. I don't expect this music to be a Bach chorale - the example is too short to tell the style - but the resolution of the seventh is in parallel octaves. Not really a great exemplar for learning basic four part harmony. – Michael Curtis Oct 22 '20 at 19:39

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