18a Discussion - Tonal Sequences

Class Discussion

Sequences

• Sequences are repeated melodic or harmonic material that is transposed up or down by a constant interval. The interval that the sequence is moved is called the interval of transposition.

• There are two types of sequences: diatonic, and chromatic. Diatonic sequences have starting notes that appear in the key you are in without needing accidentals to alter them. Chromatic sequences have an interval of transposition that is fixed and doesn’t fit the key you’re in.

• Even though some of the notes in a sequence are chromatic, if each iteration of the sequence starts on a diatonic note in the key it is a diatonic sequence and not a chromatic sequence.

• When labeling chromatic sequences you must include the interval’s quality and size.

Harmonic Sequences

• When dealing with sequences, especially when two voices or more voices are acting as melodic sequences at one time, a harmonic sequence might form. A harmonic sequence is when the roots of the chords in a progression are moving like a sequence. We only ever look at the roots of the chords in a harmonic sequence: the bass notes are usually something different than the root of the chord ( inverted).

Labeling Sequences

When labeling sequences, put an arrow in the direction that the sequence is moving (up or down), and the interval of transposition in between every iteration of the sequence. Put another arrow arching from one iteration to the next, going over the arrow and interval of transposition. Then, draw a line over the sequence and label it “seq”.

You still need to label the roman numerals correctly and every iteration must be labeled. When labeling the function of a sequence, it will always extend the function (like a tertiary function).

Class Discussion 2022

Melodic sequences

Diatonic vs. chromatic

• Diatonic is entirely in the key. The first example is completely in C, so it’s diatonic. When a sequence is diatonic you don’t label the quality of the interval of transposition because it will vary between each scale degree
• For chromatic sequences, you have to label the interval with its quality because that determines the “key”
• Always be thinking about the smallest possible pattern to identify! In example 4, the sequence can technically be a whole beat or half a beat. However, it is suggested to ID it as being half a beat because that’s simpler (especially if you’re expected to write out the rest)

Ascending vs. descending

• Intervals within the pattern will be ascending or descending, but the only thing we care about is the interval transposition, or the overall motion between each sequence. The second example is a descending sequence because the overall transposition is down by a second

Some sequences will have qualities of diatonic and chromatic sequences. Ex. 5’s inner intervals are fixed, the same as in a chromatic sequence, but the interval of transposition is a “diatonic third,” descending in thirds down the C major scale.

How to label sequences: put a bracket over the top of the areas you want to ID as a sequence, then draw arrows pointing from the one on the left to the one on the right. Over the top of the arrow, indicate whether it’s ascending/descending with an up or down arrow, and also include a number (and quality, if the sequence is chromatic) to ID the interval of transposition.

Harmonic sequences

A two voice sequence

• Is this example functional? Can you harmonize the example (come up with a progression for it)? Can we have a cadence as we normally would?
• Sequences don’t have to follow functional tonal harmony rules, which is why it’s okay for us to have a V6/4 as our penultimate chord in this example. It’s like how passing chords don’t have to follow circle-of-fifths progression rules, except it’s all the time
• Adding the alto voice
  • This also ends up being a sequence! From the second measure, the pattern is down a third + up a second, or an overall transposition interval of a second

Common sequences

• Parallel 6 chords
  • Made entirely of first inversion chords. Goal is a smooth + strong bassline
  • Always descending
• Pachelbel’s sequence
  • Suuuuuuuper prevalent, you hear it everywhere
  • This is the reason we have iii -> IV in our chord progression chart! This progression works in Pachelbel’s Canon in D and is used widely even today