Moving By An Augmented Second

Hi all!

In 4 part harmony, moving by an Augmented Second is considered dissonant, even if the interval of 3 semitones is considered consonant.

My question is :

The dissonance of an augmented second is relative to the musical scale used ?

Let's say an E harmonic minor scale for example:

If I move a voice from C to D#, it would be dissonant because I'm moving through an Augmented second.

But if I leap from E to G, it would be less dissonant because this time I'm using a minor third, even if the number of semitones remains the same (3) .

Is this right, if not can someone clarify this to me ?

Thanks!

The augmented second isn't dissonant, it's just awkward to sing. Four-part harmony arises from polyphonic singing which is why it is avoided. The C to D# movement should be avoided in the various melodic lines, but the fall or leap of it's inversion, the diminished seventh, is perfectly acceptable so long as it is followed by a change in melodic direction. The Minor Tonality is a strange beast that arises from trying to make the Aeolian Mode have similar harmonic structure to the Ionian Mode, the voice leading problems are a result of the alterations we make so the harmony has a strong tonic-dominant relationship. You could also solve your problem by raising the C to a C# by semitone thereby evoking the Melodic Minor.

However I stress that there are many regional scales around the world that make use of this interval. On example I'm fond of is the Hungarian Gypsy (Roma) Scale also called the Double Harmonic Minor. With a tonic on C it would be: C D Eb F# G Ab B C. It is quite unique in that it has a true tonic-dominant relationship between the I and V chords. It also has an augmented sixth chord (Ab-C-F# or Ab-D-F#) that can function as a predominant harmony to V. Even with this strong tonal relationship the melodies built from the scale with be rife with augmented seconds, but that is the nature of the scale. Another good scale example is the Harmonic Major which lowers the sixth by a half-step, which makes the Ionian Mode have a harmonic structure similar to the Aeolian Mode and is used for voice leading purposes the same way the Harmonic Minor is.

In short: yes, you're right

The idea of a harmonic minor is misleading. There is one minor scale which contains two pivot tones. You wouldn't go to D# from C, you would go to B. If you wanted to approach D# from below stepwise you would use C#.

Also, dissonant in this sense is a classification not a qualitative description. i.e. it isn't dissonant because of how it sounds it's dissonant because of the context and the rules being applied to it.

In short: yes, you're right

Yeah, I can be a little long winded at times.

Sorry about that.

Thank you all for your help!