Four-Chord Pop
I–V–vi–IV progression; original melody, CC0.
The "Let It Be" loop, voiced for choir.
- C
- G
- Am
- F
- C
- G
- Am
- F
- C
Bach-style harmony from your chords.
A MIDI plugin that writes four-part harmony over your chords, by rules tuned on Bach's chorales.
$35regular price $49introductory price at launch
$35regular price $49introductory price
Hear the difference
Each example plays twice: as root-position blocks, then voiced by Bock. Switch tabs while it plays.
Chromatic Mediant
I–III–IV–iv progression; original melody, CC0.
Radiohead's "Creep" chords, which Bach would never write.
- G
- B
- C
- Cm
- G
- B
- C
- Cm
- G
Figuration, embellishment and ornament
Three ways past four plain voices.
- Figuration
- The chords broken into a repeating pattern, like the opening of Bach's first cello suite. Bock voices the chords first.
- Embellishment
- Passing notes, neighbour notes and suspensions in the lower voices.
- Ornament
- The melody decorated with Bach's own figures from his organ chorales: runs, turns, mordents, trills. Every tune note keeps its beat.
Figuration: cello
Andalusian Cadence, String Crossing
i–VII–VI–V progression; original melody, CC0.
The chords rocked across the strings, as in Bach's cello suite preludes.
- Am
- G
- F
- E
- Am
- G
- F
- E
- Am
Embellishment
Silent Night, Embellished
Franz Xaver Gruber (1818). Public domain.
Passing notes, neighbour notes and a suspension in the lower voices.
- C
- G
- C
- F
- C
- F
- C
- G
- G7
- C
- G7
- C
Ornament
Greensleeves, Decorated
English traditional, 16th century. Public domain.
The tune decorated with figures from Bach's organ chorales.
- Am
- C
- G
- Em
- Am
- F
- E
- Am
- C
- G
- Em
- Am
- E
- Am
Figuration + embellishment + ornament
Amazing Grace, Everything On
Hymn tune "New Britain" (1829), words by John Newton (1779). Public domain.
A walking bass after BWV 147, passing notes, and the tune decorated.
- G
- C
- G
- D
- G
- G7
- C
- G
- D7
- G
Breaks are counted across all four voices, melody included. For figured examples, the count is for the underlying voicing.
How it works
- 1
Give it chords
Play them in from your DAW, or drop a .mid.
- 2
Add a melody
Optional. It becomes the soprano.
- 3
Get four voices
Soprano, alto, tenor and bass on MIDI channels 1–4, for any instrument.
- 4
Figure, embellish or ornament it
Optional. Break the chords into a figure, add passing notes and suspensions, or decorate the melody.
Why it sounds right
Follows the rules
Leading tones rise, sevenths fall. Parallel fifths and octaves are out.
Tuned on Bach
It matches Bach's own lower voices 66% of the time on unseen chorales.
Any progression works
Bock voices chromatic mediants and borrowed chords, and marks where a rule bends.
Repeatable
Same seed, same voicing. Raise variation to hear others.
Formats
- macOS 12 or later, Apple Silicon and Intel
- AU, AU MIDI FX for Logic, VST3, CLAP, Standalone
Questions
Is this AI?
Bock is a rule-based solver with weights fitted to Bach's chorales. It produces no audio and runs offline.
Does it make sound?
Bock outputs MIDI for your instruments. Its instrument versions can preview on harpsichord or organ.
Which DAWs does it work in?
Logic, Live, Bitwig, Reaper, Cubase and FL Studio are checked before release.
What doesn't it do?
It doesn't listen to audio, write fugues or print scores.
When is it out, and what will it cost?
$49, with a $35 introductory price at launch. The release date is not announced. The waitlist hears first.
Join the waitlist
One email when Bock ships, with the $35 introductory price.
Your address is used for that email only. Privacy