Two-part Harmony Questions

When musical performance is limited to two voices or two instruments that can only produce one tone at a time each, they will be unable between them to establish triads or more complicated chords and must therefore suggest such things.

My questions are for this small musical universe and are not for expanding the subject into other voicings and more complexities.

  1. What intervals are most common?
  2. Do the choices of intervals help to establish a “sound” like Bluegrass or Gospel or Rock or Old Time or other genres?
  3. How many different categories of Two-part Harmony are there?

Please feel free to add your own questions about this phenomenon, whether or not you have answers to already asked questions.

I just realized I’m close to ignorant on the subject in spite of having a natural appreciation for “good harmonizing.”

I think in most simple two-part harmony, the melody is sung by the higher voice with the harmonization a third below, usually.

Yes, the intervals do matter. That bluegrass sound that is identified as “high lonesome” has the higher voice harmonizing above the melody, not below, and probably more in fifths than thirds.

Yep, thirds and fifths are probably three-fifths (or more) of two part harmony intervals. I was never a good sight reader, but I can hum out a third or a fifth just out of habit.

As to the rest of your questions, I’ll let one of the fantastic music theory dopers handle them.

Thanks for those insights. As opposed to “power chords” which, as I understand them, omit the third and can therefore work in either major or minor situations by “harmonizing in fifths” (predominantly) the prevalent two-part intention is to accentuate the major vs. minor? Is that a fair interpretation of your comments?

I recall reading some liner notes on an old jazz album with Paul Desmond and Gerry Mulligan as the only melody instruments (with bass and drums filling out the quartet) where one of them commented something like, “…and at times we were blowing in thirds…” as if that was something unusual or abnormal.

Elsewhere I’ve read that some duos accentuate sixths and even sevenths, but I can’t recall what genre that applied to.

These comments of mine are to indicate to what degree I’m uninformed about these technicalities. But my curiosity is up.

I played and sang in bands for a lot of years, and it’s my impression that in pop and rock, the more common two-part harmony has the melody as the lower pitched part, particularly on choruses. FWIW, of course.

Sixths are very common, and they are related to thirds. Basically, if you sing C and E of the same octave together, that’s a third, but if you drop the E down an octave, your interval is a sixth. Generally, fourths, fifths, and octaves are “boring” intervals, and thirds, sixths, and sevenths create color and tension (and fourths when used in suspensions).

There’s a lot of different ways of creating two part harmony. Playing fifths in parallel was a very big no-no for much of classical music history, but you’ll see it in jazz, in rock guitar, country, folk, etc… You can create counterpoint, which essentially is two separate melodies that play against each other (see Baroque music, Bach’s 2-part inventions would be an ideal start for 2-voice instrumental counterpoint). Voice leading can be parsimonious (in which instruments move around musically as little as possible and often instruments stay on the same note) or it can be circuitous, in which there is no or little duplication of notes.

Fifths and octaves are generally avoided because they make a very open empty sound. Which can be useful but not as often as you might think. So, when you want to give the idea of a triad but can only use two notes, you’ll probably want to use the root and its third.

In 18th century harmony, which is the basis for most modern and pop music today, there are certain tones of a chord which are considered more important than others.

The only difference between a major and minor triad is the 3rd. In the case of a C major triad (C E G) the E is the third. A C minor triad is C Eb G. The essential components of either is the relationship between C and E or E flat. The 5th (G) is relatively non-essential. So harmony often gets by without the 5th of a triad.

Similarly, for a 4 note chord, called a 7th chord, the 5th is the least important tone and is the first to be omitted if you are short of voices.

For a dominant 7th (C E G Bb), if you are shorter still, the root is dropped and the tritone interval between the 3rd and 7th can convey enough of the flavor.

Power chords, which don’t figure much in 18th C harmony, omit the 3rd entirely, which means they cannot be called major or minor. Their ambiguity is absolute.

The blues make the 3rd into a pitch that can “waffle” or “bend” between the two intervals, or sometimes include both pitches (typically in different octaves and/or different instruments) at once. The ambiguous 3rd is a primary aspect of the blues, although not the only one.

So, to answer the OP:

1) What intervals are most common?

3rds, or their inversions, 6ths. A minor 3rd inverts to a major 6th, and vice-versa.

2) Do the choices of intervals help to establish a “sound” like Bluegrass or Gospel or Rock or Old Time or other genres?

To a limited degree; see the note on blues above. Some styles typically have a harmony line ABOVE the melody, but most is below.

3) How many different categories of Two-part Harmony are there?

I’m not sure what you mean by this other than what I already wrote.

Nicely done explanation. Covers most of my concerns.

By (3) I just meant something like: Are there more or less standard names for different varieties or flavors of two-part harmony? By that I mean does one that keeps the harmonizing voice below the melody, and uses mostly thirds, have a different name from other forms? Is that form predominantly associated with a particular genre or subgenre?

In other words, if you saw the notated parts for two-part harmony and analyzed it into its key features, would that help you establish whether the rendition would be labeled as Rock, or Country, or Blues, or “Classical” or whatever?

Also, it’s common to use the 3rd and 7th of a chord (assuming it’s a 7 chord) to define a chord.

So, for a C7, if you could only sound two notes, you’d play (or sing) the E and the Bb.

But, all of the guidelines also depend on what comes before and after whichever chord you’d looking at.

Not quite. That ‘high lonesome’ harmony sound is created by a ‘tenor line’ that is usually singing Sevenths, Octaves and Tenths (3rds an octave up). Also common are sus2 and sus4’s, providing tension and release against the primarily vocal line.

Note that bluegrass harmony often incorporates full stacked harmonies as well, with the tenor line merely being the primary counterpoint vocal line.

I often have my students think of singing a counter-melody rather than a harmony when learning to hear tenor lines.
One last thing - the other distinctive sound of ‘high lonesome’ singing is drawn from traditional yodel techniques.
professional bg picker and vocal arranger

To partly answer #2 & 3 and expand on the topic, if you heard harmony of parallel 4ths or 5ths, it would probably remind you of organum, or medieval monks singing in the chapel.

Sometimes a flurry of parallel 4ths is used to suggest an oriental sound, often as a joke.

With some exceptions, it might be hard to classify a song in those categories solely by the harmony used. It’s common in both rock and country to add more and more voices in a studio recording, both above and below a melody until the whole thing becomes a holy mess and the melody is buried. When I was transcribing music in Hollywood in the 1970’s-80’s, sometimes it was hard to tell if the melody was the top line or the 2nd line, since the mix was often so equal. I usually leaned towards the 2nd line if in doubt and if I couldn’t talk to the performer first-hand.

Two-part harmony is by definition limited. If you were asking about 4-part harmony, I could differentiate between SATB and barbershop, for example.

Perhaps the most distinctive genre would be the blues, but I think of that as more a relationship between the main or solo part and the overall, underlying harmony rather than just 2 voices. For example, a blues guitar might play a C major triad and the singer sing an E flat melody, or something inbetween an E flat and a E natural.

We’re getting into more subjective territory, here, and others might have differing opinions on styles.

As I said in my post #8 about the tritone.

Very true. The neat thing about that is that you can then drop a semitone (Eb and A) to give the sound of an F7 (fourth), inverted of course. Or you can go up a semitone (F and B) for G7 (fifth, again inverted) - hey, there’s a basic 12-bar with only two notes at a time!

For a II-V-I, again in C: F#+C (D7); F+B (G7); E+C (C) … even better, make that f# into F natural so it’s Dm7. That’s when you can play on substitutions, and invert the G7 into a Db7 - but that’s another topic for another time.