Rhythm mutator
Edit a rhythm, compare accents and swing, then export an arrangement as MIDI or a study record.
WORKING TOOLStart here
Use this workbench to separate pulse, subdivision and accent. Begin with one bar so you can hear what each change does before arranging several bars.
By the end: Compare two patterns at a known tempo and explain whether an edit changes timing, emphasis or both.
What you need: Browser audio at a comfortable level. Count “1 and 2 and 3 and 4 and” for the initial 4/4 pattern.
Before you begin: Count four steady beats and subdivide each into two. A metronome is useful.
How to use this tool
- Set meter and tempo, then edit the eighth-note steps between rest, tap and accent. Play one bar and locate the numbered beats.
- Keep A, change one feature for B and compare. Swing changes the spacing of paired subdivisions; an accent changes emphasis.
- Try the independent equally spaced layer or arrange several bars. Stop playback when finished and export the MIDI or study settings.
WORKING LAB · PULSE / ACCENT / SWING
Change the pattern while keeping count
Each cell is an eighth-note slot: a numbered beat or its “and.” Tap or press a cell to cycle through rest, normal and accent. Choose an arrangement length, hear it, then change one decision and compare. Playback does not loop indefinitely.
The lower-pitched layer divides the entire bar evenly; it does not follow the eighth-note swing grid. For 3 against 4, use 4/4, leave only numbered-beat taps on, and select 3 independent pulses.
Ready. Playback uses quiet synthesized tones.
One bar: 2.667 seconds. 8 sounding events.
First / second half of a beat: 0.333 s / 0.333 s. The total beat remains 0.667 s.
Saved B: none yet.
Study 1 · Move emphasis without moving time
Reset the example and save B. Shift A by one slot: the accents move to the “ands.” At 90 BPM, each beat remains ⅔ second, each straight eighth ⅓ second and each 4/4 bar 2⅔ seconds. Count the numbered beats even while the strong taps fall between them.
Check yourself
With swing at 50%, shift the accents to the offbeats. Did you double the tempo or make the bar longer?
Answer and reasoning
Neither. The onsets retain their spacing and the bar duration stays fixed. You changed emphasis. A listener may feel a different groove, but the measured pulse did not change.
Study 2 · Move an onset without moving the bar line
Now change only the first-half percentage from 50 to 67. The “and” moves later within each beat: about 0.447 s after its start at 90 BPM, leaving about 0.220 s before the next beat. The numbered beat stays on the same clock. This is a simple long–short swing model.
Check yourself
At 120 BPM and a 75% first half, when is the ‘and’, and when is the next numbered beat?
Answer and reasoning
The quarter-note beat lasts 0.5 s. Its ‘and’ occurs at 0.375 s and the next beat at 0.5 s. The long–short lengths are 0.375 and 0.125 s: a 3:1 ratio. Accenting an equal-timed pair cannot produce this timing change.
This is an eighth-note timing model with synthetic clicks. Human swing depends on tempo, instrument and performance; it is not universally a fixed ratio. The independent layer uses equal subdivisions of each bar, not a second tempo or swing ratio. MIDI preserves the event timing using percussion channel 10, but the receiving instrument controls timbre. A and B are temporary; export MIDI and settings to keep the work.
References: Ableton: beat and tempo · Bars. Continue with music foundations.
Change the accent, keep the clock
Tempo sets the pulse rate. Subdivision divides a pulse into smaller units. Accent makes selected events stand out. You can move accents without changing the tempo, and you can double the event rate without doubling the underlying pulse.
Work with a short repeatable pattern. First keep timing stable, then change one property. Counting aloud prevents an interesting accent pattern from quietly pulling your tempo off course.
Worked example
Original eight-slot pattern in 4/4: count ‘1 and 2 and 3 and 4 and’. Tap all eight positions evenly, first accenting the numbered beats, then accenting only the ‘and’ positions. At 60 quarter-note beats per minute, each beat lasts one second and each eighth-note slot half a second. One bar lasts four seconds.
Try it yourself
Write your answer before opening the explanation. Use the worked example if you get stuck.
Question 1
At 90 quarter-note beats per minute, how long are one beat, one eighth-note slot and one 4/4 bar? Does accenting the offbeats alter these lengths?
Show answer and reasoning
One beat is 60/90 = 2/3 second; an eighth-note slot is 1/3 second; the bar is 8/3 seconds, about 2.67. Accents change emphasis, not the durations.
Watch for: Playing every second event harder is not automatically swing. Swing changes the timing relationship between subdivisions; this lesson keeps them equal.
Summary + next step
Compare two patterns at a known tempo and explain whether an edit changes timing, emphasis or both.
Keep the result: Export MIDI for a sequencer and JSON/text for the actual settings; the receiving instrument controls the MIDI sound.
Sources and further reading
Read these references for the concepts used in the lesson.
Lesson updated 2026-09-14 · Guidance updated 2026-10-22
Coverage and further development
Edit accents, meter and swing, add an independent equal-spaced layer, arrange up to 16 bars, compare A/B and export MIDI or text.