system for computer music by samuel.freeman


The filename prefix ~g. is present for many of the loadable units that have been made available for sdfsys_b;   it is short for tildegraph.   This page introduces the tildegraph concept that has developed alongside (and within) the sdfsys environment.

First, some words about the word tildegraph; then about how a thing named tildegraph was made as a ; and then how the tildegraph concept evolved into something of an archetype for a visually founded process (or method) of soundmaking...


Etymologically, where tilde is the name for a ~, the word comes from the Latin titulus meaning title;   it can be a diacritic mark, used over a letter to change the way it sounds, such as in 'El Mañana';   or it can be used in text as an independent glyph, ASCII code number 126, such as in 'cycle~'.   A tilde character at the end of an object name in PD or Max denotes that the object is of a DSP type, owing to the tilde glyph looking like a small sinusoidal wave.   In mathematics, in logic, and in other contexts, this short wavy line has different meanings; such as to indicate equivalence, negation, alternating current, or approximation.   My interpretation of these things is that a tilde is to do with alter- and changeability.

The tilde in the word tildegraph, therefore, is meant to imply an ambiguous modification of that which is implied by the suffixing 'graph' of the word...


As a combining form in nouns, -graph denotes something written or drawn in a specified way.   In the research surrounding and leading to sdfsys, I have found it constructive to reflect on the distinction between 'graph' and 'glyph', but that is topic for discussion elsewhere.   In the present narrative it is necessary to skip to before the word tildegraph had been allocated as a name, and see about the origins of the work to which it arrived...

Building a tildegraph

I began to make things in which sinusoidal oscillators were used to modulate spatio-visual parameters over time.

My first work to fit that description, started in 2008, is called Visyn, as in 'visual synthesis', as in the synthesis of visaul patterns on screen.   Visyn was inspired by the harmonograph, and this is manifest in the way that two of the five low-frequency oscillators in the Visyn system are used (via changeable mappings) to target screen pixel coordinates over time.   The other three LFOs in the system are used to set the RGB levels for the pixel that is currently targetted.
→ more about Visyn over here.

By specifying frequencies as input to an algorithm, data is written to a jitter matrix which is then displayed on screen.   Each cell of the matrix can be mapped to a pixel (or a group of pixels) of the computer screen.   A module or unit patch named tildegraph was created for the alpha build of sdfsys.   It is the one that is seen in the video below with its matrix data colourised as blue and cyan (the data values being written to the matrix cells are bipolar in range ±1, the two hues are used to represent the two polarities).

Also in the video, above, is a module/unit patch that is loaded into another 'space' of the sdf.sys_alpha environment: the data matrix of this second module is coloured red, and is showing a trace of where a 'read-head style abstraction' has been.   The idea of a stylus abstraction comes from my conceptual model of a gramophone where that same position setting patch was used both to set the matrix cell for a poke operation (a writing stylus), and to set the matrix cell for a peek operation (a reading stylus).

By stylus I call to mind the idea of a gramophone system with a stylus needle resting on the surface of a record, and by read-head and write-head I have in mind the electro-magnetic transducers of analogue audio tape machines, but other analogies are possible too...

Work in progress - also see





dac pond


adc spiroid