Dominant seventh chord

[FireSpirit]

Hello guys!

I was studying the bass system in accordion and I realized that the dominant bass chords are composed of three pitches and not four pitches.
For example: C7 = C, E and Bb

Why did stradella bass system choose three pitches and not four? Does it have any impact on the sound/song?

If in the sheet appear "C7", I press only the button C7 or I press the C7 + G?

 

[debra]

Hello guys!

I was studying the bass system in accordion and I realized that the dominant bass chords are composed of three pitches and not four pitches.
For example: C7 = C, E and Bb

Why did stradella bass system choose three pitches and not four? Does it have any impact on the sound/song?

If in the sheet appear "C7", I press only the button C7 or I press the C7 + G?

To get a complete C7 you press the C-major and C7 buttons. (You don't press G as a base note because it includes deeper reeds than the chord notes.)
Everything is technically possible and some accordions actually have the full 4 note chord for the C7. Diminished chords also come with only 3 notes out of 4.
I have a really old 80 bass "Bianco Freres" accordion that came with complete (4 note) dominant seventh chords. (As a result you could not play diminished chords as an 80 bass accordion does not have a row of diminished buttons. Luckily it was easy to remove a note from the chords, so C7 became E-G-Bb which can double as par of G diminished.)

 

[Zevy]

Hello guys!

I was studying the bass system in accordion and I realized that the dominant bass chords are composed of three pitches and not four pitches.
For example: C7 = C, E and Bb

Why did stradella bass system choose three pitches and not four? Does it have any impact on the sound/song?

If in the sheet appear "C7", I press only the button C7 or I press the C7 + G?

If I ever want the complete dominant seventh chord, and I usually do, I will play the root, the major chord, and the dominant seventh chord. Gala-Rinni used to notate a lot of his music that way.
Good luck!

 

[FireSpirit]

Hello guys!

I was studying the bass system in accordion and I realized that the dominant bass chords are composed of three pitches and not four pitches.
For example: C7 = C, E and Bb

Why did stradella bass system choose three pitches and not four? Does it have any impact on the sound/song?

If in the sheet appear "C7", I press only the button C7 or I press the C7 + G?

To get a complete C7 you press the C-major and C7 buttons. (You don't press G as a base note because it includes deeper reeds than the chord notes.)
Everything is technically possible and some accordions actually have the full 4 note chord for the C7. Diminished chords also come with only 3 notes out of 4.
I have a really old 80 bass "Bianco Freres" accordion that came with complete (4 note) dominant seventh chords. (As a result you could not play diminished chords as an 80 bass accordion does not have a row of diminished buttons. Luckily it was easy to remove a note from the chords, so C7 became E-G-Bb which can double as par of G diminished.)

Thanks man!

Hello guys!

I was studying the bass system in accordion and I realized that the dominant bass chords are composed of three pitches and not four pitches.
For example: C7 = C, E and Bb

Why did stradella bass system choose three pitches and not four? Does it have any impact on the sound/song?

If in the sheet appear "C7", I press only the button C7 or I press the C7 + G?

If I ever want the complete dominant seventh chord, and I usually do, I will play the root, the major chord, and the dominant seventh chord. Gala-Rinni used to notate a lot of his music that way.
Good luck!

Thanks for your reply! Why the root + major chord + x7 chord and not the example that Debra wrote?

 

[Zevy]

Thanks man!


Thanks for your reply! Why the root + major chord + x7 chord and not the example that Debra wrote?

I think Paul De Bra explained that in his post.

 

[JeffJetton]

I find it makes little practical difference to me whether the 5th is in there or not.

In fact, when I play jazz piano, where I'm explicitly voicing the chords, I'll often leave it out there too. This is pretty common, especially if higher tensions like 9ths and 13ths are involved. You gotta make room somewhere, and the fifth is usually first to go.

If you think about it, of all the notes in nearly any four-note chord (tetrad), the 5th is typically the least-essential and the least-missed when absent:

Root	Establishes the fundamental tonal "base" of the entire chord and creates primary harmonic motion from and to the chord.
Third	Tells you whether the tonality is minor or major
Fifth	Just sits there being perfect most of the time
Seventh (or Sixth)	Establishes dominant-vs-major tonality and distinguishes the chord from a triad. For dominant chords, creates the important tritone interval between it and the third, providing the characteristic tension required for a dominant resolution (or authentic cadence). Also allows a dominant chords to firmly establish a key (or "key of the moment"), since that tritone interval doesn't occur in any other diatonic, four-note chord.

The exceptions, of course, are chords where the fifth is altered, such as diminished chords and #5 chords. You can get around the diminished chord problem (assuming it is a problem, which it usually isn't) by doing the old "play the root in the counter-bass and use the diminished chord button two floors down from that" trick.

For #5 chords you don't have much of a choice but to add that #5 somewhere in the right hand, in which case you wind up mighty glad the perfect fifth isn't in the chord button to clash with it!