Four-Part Writing - Ranges, Spacing, and Doubling

From this unit onward, chords get written out across four voices.

Why four? Two reasons. First, adding one note to a three-note triad creates a choice about which note to thicken. Second, a mixed chorus is already four parts: soprano, alto, tenor, and bass, abbreviated SATB.

Four-part writing is not a technique reserved for choral music. It is the format in which the rules of harmony are most visible, which is why theory training uses it.

Each voice has a range

Every part has a span of pitches it can produce, derived from what people can actually sing.

Voice	Standard range
Soprano	C4 – G5
Alto	G3 – D5
Tenor	C3 – G4
Bass	E2 – C4

Adjacent ranges overlap. The alto’s bottom limit of G3, for instance, sits inside the tenor’s range. So more than one voice can produce a given note, and you get to choose where to put it.

The working guideline is not to sit at the edges. A run of notes at the top of a range becomes punishing to sing.

Close and open position

Next, how to distribute the upper three voices. There are two types.

• Close position — soprano and tenor fit within an octave
• Open position — soprano and tenor span more than an octave

The bass is irrelevant to this. Look at the upper three voices only.

Both are correct. Close position sounds thick and focused; open position sounds broad and clear. You choose according to the moment in the piece.

Close position against open position

▶Close position▶Open position

Check: The note names are the same in both, C, E, G, and C. Only the arrangement differs. The first is compact and dense, the second spacious and transparent. The same chord takes on a different character purely from spacing.

soprano G4 and tenor C4 are a perfect 5th apart

Adjacent voices have a spacing limit

Separately from position, there is a limit on how far apart neighboring voices may be.

• soprano – alto … within an octave
• alto – tenor … within an octave
• tenor – bass … may be wider

Only the upper three are constrained; the gap between tenor and bass is allowed to open up. The reason is the overtone series. Low notes have widely spaced overtones, so packing pitches together in the bass register produces a muddy sound. Keeping the bass separated avoids that.

Check

The alto is on C4 and the tenor on B2. Is that spacing acceptable?

It depends on the chordYesNo — it exceeds an octaveIt depends on where the bass is

Check answer

Which note to double

A triad has three notes and there are four voices, so one note goes in two voices. That is doubling.

The principles are short.

1. double the root by default
2. the only note that may be omitted is the fifth
3. never double the leading tone
4. never double the seventh of a seventh chord

Rules 3 and 4 share one reason: a note with a predetermined destination cannot be doubled.

The leading tone is obliged to rise to the tonic. In two voices, both must go there, which means an octave moving in the same direction while remaining an octave. That is precisely the parallel octave covered in the next lesson.

The seventh works the same way, being obliged to resolve down by step. Two of them descend identically and produce parallels again.

Check

Which note of a seventh chord may be omitted?

the rootthe sevenththe thirdthe fifth

Check answer

Inversions change what gets doubled

“Double the root” is the rule for root position. Inversions change the situation.

In first inversion the third is already in the bass. Doubling the third again would put two of them in the chord, over-emphasizing the note that decides major or minor and skewing the sound. So in first inversion you do not double the bass note; you double the root or the fifth instead.

Second inversion is the opposite. The fifth is in the bass, and in figures like the cadential 6-4 the bass occupies a structurally important position, so doubling the bass fifth is standard.

Position	Note in the bass	Note to double
Root position	root	root
First inversion	third	root or fifth (not the bass)
Second inversion	fifth	the fifth (i.e. the bass)

Three rules, but one idea underneath: thicken whichever note is carrying the weight in that particular chord. In root position the root is the foundation; in second inversion the dominant in the bass is. Each gets doubled accordingly.

Write with the checker running

These rules turn out to be surprisingly hard to obey in practice. Ranges are easy to remember, but moving four voices while watching spacing and doubling simultaneously means something always slips.

This unit uses the part-writing checker alongside the reading. Hand it a four-part texture and it inspects ranges, spacing, doubling, and voice leading mechanically, reporting what is wrong and why.

What matters is that clearing the warnings is not the objective. Read the reason for each one and fix it while understanding why the rule exists. Once the reasons are clear, you can also judge for yourself when a rule may be broken.

▶ Open the part-writing checker Load a correct example first, then move the soprano up by one note. Hunting for the exact point where the spacing warning appears is the fastest way to internalize the boundary SATB Part-Writing Checker →

The next lesson covers the most important prohibitions in four-part writing, parallel fifths and parallel octaves. The bans on doubling the leading tone and the seventh, seen here, both trace back to them.