Now that we have all the building blocks of notes, rhythms, and chords out of the way, we can start to analyze music and the rules of putting pitch combinations together.

The way individual voices of a composition move from chord to chord is called voice leading. Back in the 17th and 18th-century, when writing music was becoming normalized, rules of voice leading came about to guide composers on how to create auditorily-pleasing compositions. This era is considered the Common Practice Period (CPP), and describes the years roughly between 1650 (Baroque Period) to 1900 (Romantic Period).

When heeding voice leading rules, any composer (or AP Music Theory student!) must take into consideration the correct chord spelling, spacing, and doubling of notes in the chords. This way, voice leading can achieve linear smoothness (there aren’t big unexpected jumps) and bring about the independence of voices (there shouldn’t be one voice that is basically copying the other voice).

Soprano-Bass Counterpoint

In this subunit, we are focusing on the relationship between the soprano and the bass lines of a typical four-part harmony. This is a chorale in four-part harmonies, composed by Johann Sebastian Bach. 

Number 6: "Christus der ist mein Leben" 

If you look in the first measure, you see that all the stems of the notes on the top in treble clef are facing upwards. This is called the soprano line. The notes also on the treble clef, but below with the stems facing down, are all the alto line. Moving to the bass clef, the notes facing up are in the tenor line, and the notes with stems going down are the bass line. 

Have you ever sung in a choir? Or at least heard something with a choir? The notes above correlate with the voices in a choir. 

SATB for short! 

Furthermore, in the chorale above, you can see the start of musical structure, with notes all leading to a fermata.

When you see these fermati in four-part writing, you know you have reached a cadence, or the end of a musical phrase. Not all cadences have a fermata, but especially in J.S. Bach's writing, or other chorales, phrases are ended by fermati. We will go into depth about cadences in Unit 4.3, so don't forget this definition!

Types of Motion

In four-part writing, the lineal movement between two voices can happen in four different ways:

1) Parallel motion: voices move in the same direction (both up or both down) by the same melodic interval. 

2) Similar motion: voice move in the same direction but not by the same melodic interval.

3) Oblique motion: one voice remains still while the second moves up or down.

4) Contrary motion: voices move in opposite directions. 

Voice Leading Rules for Outer Voices

Using the above categories, the composers of 18th-century voice leading developed guidelines for writing music in four-part harmonies. 

Good question. In the list below, remember that voice leading is how voices in one chord arrive at the next chord. Here is the beginning of the guidelines! Pay attention, these will get the money points on the AP free response questions 🤑. 

• Voice leading should proceed mostly by step without excessive leaps.
• When possible, pitches common to adjacent chords, or common tones, should be retained in the same voice part(s).
• For clarity of voice leading, any chord should maintain soprano-alto-tenor-bass (SATB) order from high to low to avoid voice crossing.
• If a perfect fifth between two voices is not immediately repeated, it should proceed to an interval other than another perfect fifth between the same voices. This applies to parallel motion (i.e., parallel fifths) as well as contrary motion; it also applies to nonadjacent chords on successive beats.
• If a perfect octave or unison between two voices is not immediately repeated, it should proceed to an interval other than another perfect octave or perfect unison between the same voices. This applies to parallel motion (i.e., parallel octaves) as well as contrary motion; it also applies to nonadjacent chords on successive beats.
• All voices should proceed melodically with the following intervals—major and minor second, major and minor third, perfect fourth, and perfect fifth. All melodic augmented and diminished intervals should be excluded, as they produce uncharacteristic dissonances. All melodic intervals larger than a perfect fifth should also be excluded, as they create uncharacteristic disjunct motion.
• The leading tone in an outer voice (i.e., soprano or bass) should always resolve up by step to avoid an unresolved leading tone
• Outer voices may include leading tones as long as those leading tones are not doubled in another voice and resolve to the tonic by ascending in stepwise motion, to avoid an unresolved leading tone.

We also need to think about the dissonances between the outer voices. In general, you should avoid dissonances between the outer voices, which would usually occur when you are writing seventh chords. Fourths between the outer voices are okay, and generally major and minor sevenths and seconds are also okay. What you really need to watch out for are augmented and diminished intervals between the outer voices – especially the tritone. 

Another thing that you should generally avoid are cross-relations, where one voice plays a note and a voice directly preceding or succeeding it plays a chromaticized version of that note. Usually, this happens in minor, when you raise the 7th. Before submitting, make sure that you don’t have a non-raised seventh near the raised seventh. 

In the AP Music Theory test, you will need to create a bass line to an established soprano line. How do I create a rocking bass line in the CCP? There are rules for this also! 

• All implied chords must allow the corresponding soprano notes to make harmonic sense.
• An acceptable harmonic progression can be made using tonic, supertonic, subdominant, and dominant triads exclusively, as long as the normative procedures of harmonic progression are followed.
• Repeated instances of a specific harmony— that is, repeating a particular chord in a particular position (root position or inversion)— are acceptable only if the repeated harmonies start on a strong beat. However, at the beginning of a phrase, the repeated harmonies may start on a weak beat.
• Melodic interest in a bass line may be created by balancing upward and downward motion and by balancing melodic steps and leaps.
• A bass line uses melodic leaps with greater frequency than upper voices or parts, which tend toward more stepwise motion.
• Allowable leaps include thirds, perfect fourths and fifths, sixths, and octaves, and, if resolved properly, descending diminished fifths.
• Octave leaps should be followed by changes in direction.
• The bass line may include successive leaps in the same direction as long as the pitches outline a triad.
• Repeated bass notes are acceptable only if they start on a strong beat. However, the repeated notes may start on a weak beat if it is the beginning of a phrase or if the second note is a suspension.
• Although bass lines may feature note values ranging from half notes to eighth notes, the quarter note is the most frequent rhythmic value

Notating the Outer Voices

Along with writing SATB chord progressions with proper voice leading, you will also have to notate chord progressions by ear, and include the corresponding figured bass. 

The big idea here is that the outer voices will provide important clues as to which chords you are hearing, so when you are trying to figure out the chords, listening to the outer voices is key. 

This seems like a difficult task. You might be wondering: “How can I figure out which voice is which?” This is why voice leading is so important. Remember that most voices, especially the top voice, move in stepwise motion. So, if you’re hearing big leaps, you’re probably hearing the wrong voice.

Once you have the top and bottom voice, you will pretty much know the chords and the inversions. If, by chance, you can’t figure it out, you should make an educated guess based on what you know about chord progressions. 

Chord Positions

Now let's get back to looking at those four-part chorales. 

There are different ways to categorize the spacing between voices on the staff. We consider them either open or closed positions. 

In a closed position, all upper voices (soprano, alto, and tenor) are placed as close together as chord tones will allow. Any other spacing is considered an open position. 

Closed position is on the left, and open position is on the right.

🦜 Polly wants a progress tracker: What are 3 guidelines to consider when writing a bass line from an established soprano line?