The name is a reference to the Koechel catalogue: the number assigned to Mozart's four puzzle canons. A puzzle canon notates only one voice. The timing and entry of every other voice must be guessed. Each performance is a working out of the rules, not a reading of them. That is the structural metaphor of K.73r. Lauren Graycar started the typeface in February 2021, though the idea had been circling longer. It began as part of a publishing project, a 28-year perpetual calendar produced through her imprint Kima. The calendar's extensive grid of repeating numbers needed a custom modular face, and Graycar wanted to draw one with as many alternates as she could think of. The rule was that every character was built from square, circle, and triangle, at uniform width, in a 3:5 ratio for x-height characters and 3:7 for cap and descender heights. Simple rules have a way of generating surprising results. A quarter circle placed above or below a square might produce the ascender of an h, the descender of a p, or the stencil component of a capital A. Each new letter opened possibilities for the ones already drawn, which meant Graycar went back… constantly. The revolving system ran for two and a half years. The cultural ground is broader than the typical Bauhaus citation. Graycar's reference points cross Eastern European typography, Slovak vernacular design, Constructivism, Cubo-Futurism, and other proto-industrial traditions. K.73r is a creative investigation that ran through many of them, across a century, finished as a functional font file in 2024. What separates K.73r from its predecessors is the production constraints of their era. The font families type table extends to over 10,500 glyphs, with up to 100 alternates per character. A designer setting K.73r is not choosing between a small set of refined options. They are navigating a system that approaches the open-ended. The hardest part, Graycar has said, was knowing when to stop. The five styles are named for their Koechel numbers. K.89a I through K.89a IV correspond to each of the four individual canons within the puzzle canon set. K.73i, the fifth, references a separate Mozart canon for five voices. The styles move from a legible base weight built for body and headline use to increasingly abstracted stencil forms where the modular construction becomes the subject of the letter rather than its scaffold. K.73r came to Public Type in 2023. Michael Cina reached out to Lauren Graycar after seeing the work and recognized what it was. The production process involved separating the five masters, addressing the kerning challenges of a family with this many alternates, and preparing files for distribution. K.73r is both functional and experimental. The base style carries running text without difficulty while the stylistic counterparts push against it, foregrounding the modular logic that the base holds in reserve. The argument the typeface makes is that legibility and experiment are not opposed. A designer using K.73r well works both ends of that line at once.