Consonant and dissonant
Unisons, 3rds, 5ths, 6ths and octaves are consonant, and so are the same intervals an octave higher (a 10th is a 3rd). 2nds, 4ths, 7ths and the tritone are dissonant. In two voices the 4th counts as a dissonance.
Species counterpoint, one note at a time
Learn counterpoint by writing it.
Write a melody against a cantus firmus. Parnasso checks every rule the moment you place a note, explains what went wrong in plain words, and plays your two voices back.
No account needed. The first stages explain every note as you write it.
1
Write
Click the staff or type A to G. Notes snap to the nearest line or space, with sharps and flats one key away.
2
Check
Every rule is checked as you go, from first species to florid counterpoint in four voices: dissonances, parallel fifths and octaves, leaps, suspensions and the cadence.
3
Listen and compare
Hear both voices on piano or strings, then compare your line with a model answer or a friend's.
The path
A route for each species. First species has seven stages, from your first line above a Dorian cantus to the Phrygian cadence. Each stage has three exercises, and the first stages guide you note by note.
Teaching a class?
Set counterpoint homework that marks itself, and see who is done and where the class got stuck.
Questions
What is species counterpoint?
A step-by-step way of learning to write independent melodies that sound good together. Johann Joseph Fux set it out in Gradus ad Parnassum (1725), and composers from Haydn to today have trained on it. It moves through five "species", from one note against one note to free florid writing.
What is a cantus firmus?
A fixed melody, usually in whole notes, that moves mostly by step and ends on the final of its mode. You write a second line above or below it.
What are the rules of first species?
Every interval between the voices is a consonance. You begin and end on a perfect interval, avoid parallel fifths and octaves, approach perfect intervals by contrary motion, move mostly by step, and close with a cadence that raises the leading tone. Read all the rules.
Who is Parnasso for?
Composition and music theory students, self-taught composers, and teachers who want exercises that mark themselves.
What does it cost?
Every lesson, writing a cantus firmus and first species in all six modes are in the Free plan. Second to fifth species and counterpoint in three and four voices are part of Solo. Students in a teacher's class get everything through the teacher's plan. See Pricing.
Ten minutes, one exercise.
Parnasso for teachers
Counterpoint homework that marks itself.
Set an assignment in two clicks. Your students write it in the browser, every rule is checked as they go, and you see who is done and where the class got stuck.
18handed in
11all correct
6still writing
4not started
- Emma M.Handed in
- Lucas K.Handed in
- Lia P.Still writing
- Noah T.Not started
What you get back
Less marking, more teaching. Five things that change when counterpoint homework checks itself.
Marking
Every exercise marked, every rule, every time.
Parallel fifths, unprepared dissonances, leaps that are never recovered: Parnasso checks them all, as your students write. Nothing slips past, and nothing waits for your pen.
Parallel fifths Bars 4 and 5 both have a perfect fifth between the voices, and both voices move in the same direction. Change one of the notes.
Insight
Know where the class is stuck before the lesson.
See the mistakes most of your students made, ranked. Spend the lesson on what the class actually got wrong, not on what you guess.
- Parallel fifths18
- Leap not recovered13
- Unprepared dissonance9
- Repeated note4
For the next lesson Parallel fifths: bars 4 to 6 of exercise 3.
Preparation
A full assignment in two minutes.
Choose the species, the stage and how many exercises. Parnasso writes them, in the modes you pick, and you can open and play each one before you give it out.
First speciesContrary motion× 3
Second speciesPassing tones× 2
- 1Dorian, above
- 2Aeolian, below
- 3Ionian, above
- 4Dorian, above · 2 : 1
- 5Mixolydian, below · 2 : 1
Live coachingCheck onlyDue Fri 24 Oct
Practice
More practice, and answers while the student is still thinking.
A student placing a note at eleven at night gets the explanation at once, not at next week’s lesson. They try again right away, so more happens between lessons.
On papernext lesson
On Parnassoas each note is placed
11:42 pm · Lucas · bar 4 The 5th in bar 4 follows another 5th. Try a 3rd or a 6th above the cantus.
Control
Your teaching stays yours.
Choose live coaching or marking only after the student presses Check. Read each student’s line, exercise by exercise, and leave a note in your own words. Parnasso checks the rules; you keep the musical judgement.
12345
Your note to Lucas
Good line in bar 3. In 5, check the cadence: the leading tone needs to rise.
What your students get
- Nothing to buy. Students in your class get every feature through your plan, for as long as the class runs.
- One sign-in. They join with the email you added, or with the code. No separate accounts to manage.
- Their work is saved. They can stop in the middle of an exercise and continue on another device.
- They keep practising. After the class, the lessons and first species stay open to them.
Simple pricing
$15 a month or $45 a semester, for up to 40 students across all your classes. Need more? Studio covers 120.
Questions teachers ask
Do my students need to pay?
No. Students in your class get everything while the class runs. They sign in with the email you added, or with your class code.
What do I need to start?
An email address and two minutes. Make an account, make a class, paste your students’ emails or share the invite link, and set a first assignment.
Can I write my own exercises?
Not yet. You choose the species, the stage and how many; Parnasso builds the exercises, and you can open and play each one before you give them out. Fux’s six cantus firmi are available in the practice room.
How is it marked?
The rules of counterpoint are checked by code, so a parallel fifth is always caught and never guessed. Parnasso also comments on the shape of the line. It does not replace your ear: use the results to decide what to talk about.
Who can see my students’ work?
Only you and the student. Work is stored in the student’s account and is deleted if they leave the class or you remove them.
Which levels does it cover?
Writing a cantus firmus, the five species in two voices, and counterpoint in three and four voices, in six modes.
Your next assignment, in two clicks.
The path
Routes in Fux's order: writing a cantus, the five species, then three and four voices. Every stage has three exercises: solve all three to open the next.
Write a line above the cantus
New exercise
Species
Mode
Cantus
Voices
Dimmed options are included in Pro: the Solo, Teacher and Studio plans, or a teacher’s class. See the plans
Cantus in the
Your line goes
Clefs
Or open a friend's challenge
Keyboard shortcuts
Show allowed notesH
Note input on or offN
Write a note and move onA–G
Repeat the previous noteR
Choose a bar← →
Move note a step↑ ↓
Move note an octaveCtrl/⌘ + ↑ ↓
Eighth, quarter, half, whole3 4 5 6
Dotted note.
Tie over the barline (break a tie in fourth species)+ or T
Natural, sharp, flat7 8 9
Sharp, flat, natural= - 0
Remove note⌫
Undo, redoCtrl/⌘ + Z, + ⇧ Z
Play or stopSpace or P
Leave note inputEsc
Note values and accidentals follow Sibelius's keypad (3–6, 7 8 9) and Dorico's keys (= - 0); octave moves work as in Sibelius, Dorico and MuseScore.
Learn counterpoint
Five species, each a small step up from the one before, as Johann Joseph Fux set them out in Gradus ad Parnassum (1725). Start with the basics: they hold in every species.
Two lines, one given
You get a fixed melody, the cantus firmus: whole notes, mostly by step, starting and ending on the final of its mode. You write a second line above or below it. The rules on this page apply in every species; each species then adds its own.
Intervals
Begin on a perfect consonance
Above the cantus: unison, 5th or octave. Below it: unison or octave only, so the mode stays clear.
End on a unison or octave
And use the unison nowhere else: in the middle the two voices merge into one.
The cadence
Close with a major 6th opening to an octave (line above) or a minor 3rd closing to a unison (line below). In every mode except Phrygian this means raising the leading tone, here C to C♯.
Motion between the voices
No parallel 5ths or octaves
Two perfect intervals of the same size in a row, with both voices moving, make the voices lose their independence. Parallel 3rds and 6ths are fine.
No direct 5ths or octaves
Approach a perfect interval by contrary or oblique motion, never with both voices moving the same way.
Keep the voices apart and in order
No crossing: the upper line stays above. Keep them within a 10th of each other where you can.
Prefer contrary motion
More than three 3rds or 6ths in a row, or too many bare 5ths and octaves, make the two lines sound like one.
Shape of the line
Move mostly by step
Allowed leaps: 3rds, perfect 4ths and 5ths, the rising minor 6th and the octave. Avoid the tritone, 7ths and augmented intervals: they are hard to sing.
Recover from leaps
After a large leap, step back in the opposite direction. Avoid two leaps in the same direction.
One climax
Give the line one highest note, away from the cantus's high point, and keep its range singable: within a 10th.
Don't outline a tritone
When the line runs in one direction from F up to B (or down from B to F), the ear hears the tritone between its ends, even though every move is a step. Turn back before you reach it, or carry on past it.
The modes
Six church modes
Dorian, Phrygian, Lydian, Mixolydian, Aeolian and Ionian, on several finals each. Stay inside the mode. The only chromatic note is the raised leading tone at the cadence; Phrygian never raises it.
One line
Writing a cantus firmus
Before writing against a cantus, write one. A cantus firmus is a short, plain melody in whole notes: it sets out the mode, moves mostly by step and has a clear arc. Every species exercise starts from one.
Begin and end on the final
The first and last notes are the final of the mode, in the same octave. That is what makes the mode clear.
Approach the final by step
Usually from the note above. A step up from the leading tone below also works, but the cantus itself stays in the mode.
Mostly steps, a few leaps
One to three leaps give the line character. After a leap, step back the other way; never two leaps in a row.
One climax, a singable range
The highest note comes once, somewhere in the middle. Keep the whole line within about a 10th, with no repeated notes and nothing outside the mode.
1 : 1
First species
One whole note against each note of the cantus. With no rhythm to hide behind, every interval counts. All the basics apply, plus two rules.
Every interval is consonant
No dissonances at all: each bar is a unison, 3rd, 5th, 6th or octave, or a compound of these.
Avoid repeated notes
With one note per bar, a repeated note stalls the line. Move on, by step if you can.
2 : 1
Second species
Two half notes against each cantus note. The line opens with a half rest and ends on a whole note. The second half of a bar can now carry a dissonance, if it passes.
Downbeats are consonant
The first half note of every bar follows the first-species rules for harmony.
Weak beats may pass
The second half may be dissonant only as a passing tone: reached by step and left by step in the same direction, filling in a 3rd.
Watch the downbeats
5ths or octaves on two downbeats in a row are heard as parallels, even with a note between them.
Keep moving
No repeated notes. The cadence sits on the last half note: a major 6th above, or minor 3rd below, then the final.
4 : 1
Third species
Four quarter notes against each cantus note, opening with a quarter rest. The downbeat is consonant; the other three quarters may be dissonant, handled in one of three ways.
Passing tone
On any of the three weak quarters: reached and left by step in the same direction.
Neighbour note
On the 2nd or 4th quarter: a step away from a consonance and straight back to it.
The cambiata
On the 2nd quarter: step down to the dissonance, leap a 3rd down to a consonance, then step up. The one dissonance in species counterpoint that is left by leap.
The rest still holds
No repeated notes, no parallels across the barline, no 5ths or octaves on successive downbeats.
Ties
Fourth species
Half notes, shifted: each note is struck on the second half of the bar and tied over the barline into the next downbeat. When the cantus moves under the tie, you get a suspension.
The struck note is consonant
It resolves the last suspension and prepares the next one.
A dissonant tie resolves down by step
Above the cantus use 7–6 or 4–3; 9–8 sounds hollow. Below the cantus use 2–3.
A consonant tie is free
If the tied note is consonant against the new cantus note, the next note may step or leap.
The cadence
The classic 7–6 above (2–3 below), resolving to the octave or unison, with the leading tone raised.
Breaking the species
Sometimes no tie leads anywhere good: every suspension would make parallels or an unresolvable dissonance. Then Fux breaks the chain for one bar: the note is not tied, and the next bar starts with a fresh, consonant note, as in second species. Use it once at most. In Parnasso, select the note and press + to break or restore its tie.
Florid
Fifth species
All the species mixed, bar by bar: halves, quarters, a pair of eighths, and ties that make suspensions. Choose a rhythm for each bar, then write the notes.
Each note keeps its own rule
Struck downbeats are consonant. Dissonant halves pass; dissonant quarters pass, neighbour or form a cambiata; dissonant ties resolve down by step.
Eighths move by step
In and out, usually as a pair on the 2nd or 4th quarter of the bar.
Decorating a resolution
In florid counterpoint a suspension may be ornamented before it resolves: short consonant notes after the tie, most often a 3rd down and back up, as long as the step down arrives by beat 4.
Dotted notes
A dotted quarter and an eighth, or a dotted half and a quarter, give the line a lilt. Dotted notes start on a beat; the eighth after a dotted quarter moves by step. Press . to dot the selected note.
Vary the rhythm
The same rhythm three bars in a row sounds like a lower species. Let the line speed up and slow down.
3–4 voices
Three and four voices
After the five species in two voices, Fux adds voices. The cantus may sit in the bass, the middle or on top; the other voices move note against note, or one of them in a higher species. Every rule still holds between every pair of voices, and each chord is now heard from the bass.
Hear every chord from the bass
A 4th above the bass is a dissonance. Between two upper voices it is fine: in C–G–C the G and C make a 4th, but each is consonant with the bass.
Full chords
In the middle of the exercise, give each chord a 3rd (or a 6th) above the bass. Don't double the raised leading tone. A tritone between upper voices is allowed but tense.
Parallels between every pair
No parallel 5ths or octaves between any two voices. Direct 5ths and octaves matter most between the outer voices, when the top voice leaps.
First and last chords
The bass stands on the final. Above it: the octave, the 5th, or the 3rd. The last chord may close with a major 3rd.
The cadence
One voice rises from the raised leading tone to the final, as in two voices; when the bass is free, it often leaps from the 5th to the final.
A little more freedom
With more voices, a repeated note, a unison or a brief crossing is sometimes the best way through. Use them sparingly; Parnasso marks them as suggestions, not errors.
One voice in a higher species
When one voice moves in halves, quarters, ties or florid rhythm, it follows that species' rules against every other voice; the rest move note against note.
Pricing
In a teacher's class? Your teacher's plan covers you. Sign in with the email your teacher added and everything opens for as long as the class runs.
Free
To start, and to learn the rules.
$0
Start practising
- Every lesson, with examples to hear
- First species in all six modes, unlimited
- Fux's six cantus firmi, or a new one each time
- The seven-stage first-species path
- Writing a cantus firmus
- Rule checking, hints and model answers
Solo
For learning on your own.
$6 / month
or $19 a semester
- Everything in Free
- Second, third, fourth and fifth species
- Three- and four-voice counterpoint, with the cantus in any voice
- Unlimited new exercises in every species
- Sixteen more stages on the path
Teacher
For one teacher and a class.
$15 / month
or $45 a semester
- Everything in Solo, for you and every student
- Up to 40 students across all your classes
- Students join with their email or a class code
- Assignments in two clicks: Parnasso writes the exercises
- Live coaching, or marking after the student checks
- A class view: who is done, and the mistakes most of the class makes
Studio
For a larger studio.
$35 / month
or $99 a semester
- Everything in Teacher
- Up to 120 students across all your classes
- A student in two of your classes uses one place
School or conservatoire
Several teachers, more than 120 students, or an invoice for your department? Tell us what you need and we will put a plan together.
About Parnasso
A practice room for composers who learn on their own and have no teacher to mark their exercises.
Every exercise is short: a cantus firmus and a line to write against it. The rules of counterpoint are checked by code, so a parallel fifth is always caught and never guessed. On top of that, Parnasso comments on the shape of your line: its climax, its leaps, how independent it is from the cantus.
The name comes from Mount Parnassus, home of the Muses. In 1725 Johann Joseph Fux called his counterpoint textbook Gradus ad Parnassum, "steps to Parnassus": a climb toward mastery, one exercise at a time. That book taught Haydn, Mozart and Beethoven. Parnasso follows the same path, starting with counterpoint and climbing toward harmony and beyond.
Credits
Piano, cello and violin samples from tonejs-instruments (MIT licence). Playback by Tone.js. Notation engraved with VexFlow (MIT) in the Bravura music font (SIL Open Font License). The opening exercise uses Fux's Dorian cantus firmus.
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Data is stored with Supabase in the European Union (Frankfurt). The site is served by Cloudflare. Sign-in emails are sent through our email provider.
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You can use Parnasso without an account. To see or delete what we hold about you, or to leave a list, write to us through the contact page and we will do it within 30 days.
Last updated 18 October 2026.
Terms of use
The short version: use Parnasso to learn, be kind with challenge links, and know that it is a beta.
The service
Parnasso is provided as it is, during a beta. Rule checking follows the common textbook rules of species counterpoint after Fux; teachers and textbooks differ on details, so treat its feedback as guidance, not a final grade.
Your work
The lines you write are yours. When you share a challenge link or image, you allow anyone with the link to see that exercise.
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Keep access to your email account safe: it is how you sign in. We may suspend accounts that abuse the service, for example by flooding challenge links or lists.
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Changes
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Last updated 18 October 2026.
Contact
Found a wrong rule, a bug, or an idea for the next exercise? Tell us.