First Species · Theory

Note Against Note Second Species Cantus Firmus Parallel Fifths and Octaves Consonance and Dissonance

First species is the strict training stage of note against note: one note to one note, every step accountable. It teaches exactly one thing — making "which interval goes here" automatic.

The two core rules

One: perfect consonances are the frame, imperfect ones the flow.

Class	Intervals	In first species
perfect consonance	unison, octave, fifth, fourth	used at the start and end (structural points)
imperfect consonance	major/minor thirds and sixths	used internally (flowing points)
dissonance	seconds, sevenths, tritone	forbidden in this species

Why the split? Because perfect consonances are too stable: use them continuously and the music sounds like a string of cadences, so you can no longer tell where the real ending is. Structural points therefore occur only at the opening and close (with the occasional interior pivot), while thirds and sixths do the walking (see consonance and dissonance).

Two: avoid parallel and hidden fifths and octaves.

Perfect consonances must not appear consecutively (see parallel fifths) — the two voices fuse into one and the texture loses a voice. Hidden fifths and octaves (arriving by similar motion with a leap in the upper voice) are avoided too.

The order to check your work

This is the most practical part — check in a fixed order, never by feel:

Order	Check	What failure looks like
1	is the vertical interval legal at every step?	a second or seventh in the middle
2	do start and end land on perfect consonances?	ending on a sixth, so it sounds unfinished
3	any consecutive perfect consonances?	two fifths in a row
4	direction of the two lines	similar motion throughout, especially with leaps
5	does each line work as a melody when sung alone?	repeated wide leaps, or jumping back and forth

The fifth matters most and is the most forgotten. A setting that passes the first four and yet yields no singable line in either voice is "all correct" on the checklist and a failure in music (see counterpoint).

Diagram: structural points and flowing points

Listen: frame versus flow

First species is a two-voice exercise and cannot be played here. Use interval to compare a structural interval with a flowing one: hear the fifth (perfect, stable), then the third (imperfect, mobile). First species trains choosing the right one at the right moment.

Common misconceptions

"First species is just a beginner exercise." The distinction it teaches — frame versus flow, perfect versus

imperfect — runs through all harmonic writing.

"More perfect consonances is safer." They must not be consecutive, and consecutive use blurs the tonal

centre.

"If every interval is legal, the writing is correct." The fifth test is decisive: each line must sing.
"Too many rules, too rigid." Every rule names an audible consequence — voices fusing, the ending

disappearing, a line that stops being melodic. Not taste, consequence. :::

Listen in the library

Invention 1C11:03Bach's first two-part invention — the entry passage is close to note against note, useful for checking each intervalDetailsSound Ye the Trumpet CallC10:35An organ hymn — four voices changing together, the same texture family as first speciesDetailsScales, Arpeggios, and CadencesC13:22Scale and cadence exercises move in equal note values, ideal for practising step-by-step interval checkingDetails

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

Sources

第一类对位（一音对一音）的规则：起止用完全协和、内部以不完全协和为主、避免平行与隐伏五八度，为通行对位教学体系
完全协和作骨架、不完全协和作流动这一分工，与和声学的协和分级同源

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

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