Identifying pentatonic scales

They are simple but not always easy

It's pentatonic scales week in aural skills class. This would seem to be the easiest thing on the syllabus, but I discovered while doing listening exercises with the students that even these simple scales have their subtleties.

Major Pentatonic

You can understand the C major pentatonic scale to be the C major scale without scale degrees four and seven. These are the ones that create all the tension and dissonance, and without them, the major pentatonic sounds uncomplicatedly sunny and cheerful. (Or does it? More on that in a minute.) Click the image to play the scale in the aQWERTYon.

You can easily explore the G-flat major pentatonic scale: it's the black keys on the piano. Guitarists will find that G major pentatonic is particularly easy to play. (Too bad they can't so easily play it with the pianists.)

Cultures around the world use the major pentatonic scale and it is unfathomably ancient. In Werner Herzog's documentary Cave of Forgotten Dreams, a paleontologist plays a replica of the oldest known musical instrument, a flute made from a vulture bone. It's tuned to E major pentatonic.

Major pentatonic is ubiquitous in American popular culture. "My Girl" by the Temptations begins with a guitar riff that walks up the C major pentatonic scale, and the melody is built entirely from the scale as well.

While the melody sticks to the pentatonic scale, the underlying chords and other accompaniment do not. We will talk about why at the bottom of the post.

Many traditional folk songs and spirituals use major pentatonic too. Paul Robeson's recording of "Nobody Knows The Trouble I've Seen" is in C major pentatonic (though again, the chords use many notes from outside the scale.)

My students had trouble immediately identifying this song as major because it's so sad. Everything else being equal, major keys tend to sound happier than minor ones, but other musical factors can easily outweigh tonality: tempo, rhythm, phrasing and lyrics. Other major pentatonic tunes that can register as sad include "Amazing Grace", "Swing Low, Sweet Chariot", and "This Train Is Bound For Glory".

"Starfish and Coffee" by Prince is an intriguing edge case. The vocal melody is in A major pentatonic... sort of. 

Prince sings his C-sharps extremely flat, closer to C-natural. But they aren't minor thirds either, they are blue thirds, right in between. The melody has a few other blue notes in it as well. Pentatonics have an intimate relationship to the blues.

Minor Pentatonic

C minor pentatonic is the C natural minor scale without the second and sixth degrees. You can also understand it as a rotation of Eb major pentatonic starting on C. (By the same token, C major pentatonic is a rotation of A minor pentatonic starting on C.) Like its major cousin, minor pentatonic is heard in musical traditions from around the world.

Funk is built on a foundation of minor pentatonic. The clavinet riff that begins Stevie Wonder's "Superstition" is in E-flat minor pentatonic, as is the verse melody.

Minor pentatonic is great for conveying strength and conviction, as in Sweet Honey in the Rock's recording of "Eyes on the Prize."

Just like major pentatonic doesn't necessarily equal "happy", minor pentatonic doesn't necessarily equal "sad." The melody of "Sonnymoon For Two" by Sonny Rollins is a straightforward walk down the B-flat minor pentatonic scale, and it's one of the most joyful tunes in the world.

Mountain Modal

Major and minor pentatonic are rotations of the same scale necklace, and they are not the only two possible ones. If you play the major pentatonic scale starting on its second degree (i.e. start C major pentatonic on D), you get a scale that is sometimes called "mountain modal." It does not have a major or minor third in it, giving it a fascinating ambiguity. Adam Neely recommends that you listen to "West Virginia Mine Disaster" by Jean Ritchie, which uses C mountain modal (B-flat major pentatonic starting on C).

"Little Margaret" is another beautiful traditional tune in mountain modal, sung here by Rhiannon Giddens. She is singing in C mountain modal (B-flat major pentatonic starting on C.)

Mountain modal makes a nice guitar or banjo tuning that pairs well with minor pentatonic. Here's Tim Eriksen singing "Sugar Baby" in D minor pentatonic. When he strums the open strings of the banjo, you can hear the D mountain modal tuning.

Pentatonic Chords

I said above that many pentatonic melodies have non-pentatonic accompaniment. The C major pentatonic scale can only produce two triads, C and Am, and that is not much to work with. Without 4^, you can't make a IV chord, and without 7^, you can't make a V chord. The C minor pentatonic scale can only produce Cm and Eb. Meanwhile, pentatonic melodies are very easy to harmonize if you take advantage of all the diatonic, modal, jazz and blues chords, so that is what songwriters and arrangers tend to do.

On the other hand, if you don't limit yourself to triads, then pentatonic scales themselves can produce some interesting harmonies. If you order the major pentatonic by perfect fourths (E to A to D to G to C), then you get a gorgeous chord. What should you call it? If you think of C as the root, then it's C6/9. You could also consider A to be the root, in which case it's Am11. I prefer to think of it as "the fourths chord", because that symmetrical stack of fourths is more important to the chord's sound than whatever major-ness or minor-ness it possesses. McCoy Tyner plays a ton of fourths chords; for example, listen to his playing on John Coltrane's recording of "My Favorite Things". Fourths chords are also easy to play on the guitar. And you can rearrange fourths chords to make sus2, sus4, 7sus4 and 9sus4 chords; read more about those here.

Because the pentatonics are so easy to play on various instruments, they are a natural vehicle for improvisation. You can't necessarily play an "interesting" melody with them in terms of pitch content, but this is a positive. If you are feeling uncertain about improvising, it's nice to know that you can't play any "wrong" notes. If you are a more advanced improvisor, you can take the limited pitch possibilities of the pentatonics as a valuable creative constraint: focus your attention on rhythm, phrasing and form.