Triangle / Lambdoma
This instrument uses fractions to make a wide palette of just intonation intervals available all at once.
The rows display the overtone series (1/1, 2/1, 3/1 ...). The columns multiply out the undertone series (1/1, 1/2, 1/3, ...). The resulting intervals are instantly musically meaningful, though they arise from simple ratios.
Color indicates position in the octave, with red being the root or unison interval 1/1. Brightness indicates octave, with white and black tending toward the extremes of human hearing.
- The default instrument is a Hokema sansula, a type of kalimba.
- Right-click notes to turn on sine waves matching the interval.
- Drag-and-drop samples into the window to play with your own sounds.
keyboard shortcuts
| ESC | Stop all sound |
| ESC ESC | Return to home position |
| ? | Show this help |
| + - | Change scale |
| up down left right |
Scroll the grid |
| 0-9 a-z | Keyboard mapped to the top-left 8x8 grid, sorted by pitch |
| ? | Toggle this help |
| \ | Detect MIDI device (listening on channel 1) |
| ⇧ + ⇧ - |
Change scale root by +/- 1 hz |
| ⌘⇧ + ⌘⇧ - |
Change scale root by +/- 10 hz |
| ⌘ up ⌘⇧ up ⌘⇧⌃ up |
Change pitch of sampler by +10 / +1 / -0.1 hz |
| ⌘ down ⌘⇧ down ⌘⇧⌃ down |
Change pitch of sampler by -10 / -1 / -0.1 hz |
scales
Alternate scales are accessed by pressing the +/- keys:
| natural | Natural numbers: 1, 2, 3 ... |
| undertone | Subharmonic intervals under the line 1/1 |
| overtone | Harmonic intervals above the line 1/1 |
| primes | Prime numbers only (most dissonant) |
| arithmetic | Multiply all cells by an interval rather than scrolling |
| Collatz | Hailstone numbers of Lothar Collatz |
| Pythagorean |
Pythagorean intervals
where each ratio is a power of 2 |
about this page
This webpage was inspired by Peter Neubäcker, inventor of the Melodyne software. In the short biographical documentary Wie klingt ein Stein? (What does a stone sound like?), Neubäcker describes the basic principles of harmonic intervals. He first demonstrates how one plays harmonics on a monochord. He then shows it next to a grid of whole-number ratios, and demonstrates how one can use these intervals to find specific ratios. I had never seen just intonation demonstrated so elegantly, so I made this page to explore the concept interactively.
I later learned that I had constructed the "lamboid diagram" or Lambdoma, named for its resemblance to the Greek letter Lambda. The synergy of color and sound in the Lambdoma, linking the octave to the color wheel, was studied in depth by artist and sound practitioner Barbara Hero. Hero made the Lambdoma her life's work, and built an 8x8 electronic Lambdoma instrument for sound healing purposes.
Hero learned of the Lambdoma from Tone: A Study in Musical Acoustics (1968) by Levarie and Levy, who trace the Lambdoma back to Pythagoras (ca. 500 BCE) by way of the Introduction to Arithmetic by Nicomachus of Gerasa (ca. 100 BCE) and the Theologumena arithmeticae of Iamblichus (ca. 300 CE). The Lambdoma is also mentioned by Plutarch in his commentary on Plato's Timaeus. It has been rediscovered several times, including in the 19th century by Albert von Thimus, who depicts it in Die harmonikale Symbolik des Alterthums (1876). The Lambdoma was also used by mathematician Georg Cantor in his theory of transfinite sets (see below). More information can be gleaned from Hero's paper, The Lambdoma Matrix and Harmonic Intervals (1999).
the mathematics of perception
With the root, fifth, fourth, and octave in the top-left corner, the Lambdoma shows how the 3:2 proportion is essential to human perception.
Mapping colors logarithmically to this wheel of fractions between 1 and 2, with red at the octave (1:1), it naturally follows that the fourth (4:3) is green, and the fifth (3:2) is blue. These ratios seem to correspond to the photoreceptors in the human retina, which are sensitive to wavelengths of light in three different ranges: long, medium, and short. These ranges are perceived as "red, green, and blue" in the brain, yet our mind's eye sees a continuous cycle of color that loops back on itself.
The musical circle of fifths, derived from repeatedly stacking the 3:2 proportion, can be studied in more detail in this program's Pythagorean scale mode. Similar notes can be found by color and compared. One can easily hear how stacked fifths overshoot the octave by finding two far-apart red notes and playing both at once, which makes them beat against each other. This interval is the "syntonic comma" which is averaged out in various keyboard tuning systems.
Tuning systems must weigh the harmony of pure intervals against musical versatility. A Pythagorean tuning system made from pure fractions will include many different "fifths" and "thirds" at different points in the scale, which makes each musical key sound highly distinctive. Some intervals are extremely dissonant and harsh, rendering certain keys unplayable.
12-tone equal temperament enables musicians to play in any key by
bending all of the notes slightly out of tune. This process invokes
irrational numbers, and creates in-between intervals which do not
exist anywhere in the Lambdoma, no matter how far out you go.
Equal-tempered semitones are separated by a ratio of the 12th root of
2 (1:
In the Lambdoma, Barbara Hero also sees the image of Georg Cantor's transfinite set of rational numbers ℚ, which Cantor proved countably infinite by arranging fractions along two axes by numerator and denominator, similar to the Lambdoma. One may easily grasp this countable infinity of rationals by considering that, while there are infinitely many fractions, in between any two there lies an uncountable continuity of real numbers in ℝ.
thank you!
Sansula samples by Freesound user cabled_mess. Thanks to Dave Noyze for telling me about Barbara Hero. Thanks to Hems for the support!
Jules LaPlace / asdf.us / 2018-2025