Second Species · Theory

First Species Third Species Note Against Note Non-Chord Tone Treating Non-Chord Tones

Second species inserts one note between the steps of first species:

For each step of the cantus firmus, the counterpoint moves twice. The note on the weak beat may now be dissonant.

The one new variable: the weak beat

In first species every note had to be consonant, which made the texture step-locked. Second species frees precisely the weak beat:

Position	Requirement	Why
strong beat	must be consonant	the strong beat is a structural point; the ear counts it
weak beat	may be dissonant (by step)	the weak beat is a joining point; passed over quickly, it is not heard as an arrival

The principle behind the relaxation is exactly that of harmonic rhythm: strong beats carry the frame, weak beats carry the connection. Which is also why the dissonant weak-beat note must enter and leave by step (otherwise it will be heard as a chord tone — see treating non-chord tones).

Three rules worth watching

One: the weak-beat dissonance must be a passing note. It is safest when both voices move by step in the same direction; if it is approached by leap, it immediately sounds like an error.

Two: do not fill every weak beat with a passing note. Filling everything removes the texture's breathing and in effect turns it into third species (see third species). Deciding where to leave space is itself a compositional judgement.

Three: the two voices should be offset, not stacked. If both always change pitch at the same instant, second species degenerates into "first species with a tail".

Its relation to note-against-note writing

Second species is not a separate system but the first relaxation of note-against-note writing:

First species trains "every step right"; second species trains "when you may stop being quite so right".

The pattern recurs throughout the training: relax one constraint at a time, and supply a rule to manage it. Freeing the weak beat comes with the rule "pass by step".

Diagram: the division of labour between beats

Listen: consonant next to dissonant

Second species is a two-voice exercise and cannot be played here. Use interval to compare the two intervals that will appear on strong and weak beats: a third (consonant, can be structural), then a second (dissonant, passing only).

Common misconceptions

"Weak beats can hold any dissonance." It must be a passing dissonance approached and left by step. A

leap into a dissonance sounds like a mistake.

"Filling every weak beat is better." That removes the breathing and effectively moves into third-species

writing.

"The strong-beat rule was relaxed." It was not. Strong beats must still be consonant; only the weak beat was

freed.

"Second species is easier than first." More variables are in play (strong beat, weak beat, and the rhythmic

relation between the two voices); it is merely more flowing. :::

Listen in the library

Invention 08C11:06Bach's eighth two-part invention — passing notes on weak beats are clear, showing the strong-stable, weak-moving divisionDetailsOde to JoyC10:37The Ode of Joy theme — passing notes in the stepwise motion keep the line flowing, against the skeletal chord tonesDetailsScales, Arpeggios, and CadencesC13:22Scale and cadence exercises in equal note values show how the texture changes once weak beats are freedDetails

All tracks from midicn-lib — inline badge is the license tier (C1 commercial / C2 non-commercial / C3 study only).

Sources

第二类对位（二音对一音）规则：强拍须为协和音、弱拍可用级进经过的不协和音，为通行对位教学体系
弱拍放宽与和声节奏的原理一致（强拍承载骨架、弱拍承担连接），为通行表述

Used for fact-checking only; all prose is original.

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