The Gridder is an instrument that focuses on micro-tonality in various ways. It consists of a scaleable grid of nodes (from 5 to 48 squared) which is mapped in equal temperament (implementing the formula fundamental * 2.pow(i/steps_per_octave)) in octaves (one octave per horizontal line) but wrapping at a set ceiling frequency.

Like SoundScratcher, the Gridder is a broad conceptual environment on its own that affords various interaction modalities. We could divide the analysis of the instrument into two parts: the environmental part – where we look at the acoustic properties of the instrument; and the interaction part – where we focus on how the instrument can be controlled.

Looking at the environmental properties of the instrument, the most important part is the definition of the pitch resolution in an octave. The grid can be scaled from a 5-tET scale to 48-tET scale. (5-tET = 5 tone equal tempered tuning). Each node on the grid is a note in the scale. The horizontal axis represents the N notes in the octave and the vertical axis is the next pitch range, by default octave above, but could be the fundamental scale transposed by a 3rd, a 5th or any other relation. There is a setting that controls maximum frequency on the vertical axis forcing the scale to wrap back to the fundamental note when the ceiling is reached. The user can define scales in any of the pitch resolutions by drawing vertical lines as represented by the columns of boxes in Figure 4 and these can be stored in a dictionary.

There are 8 different types of synthesized sound that can be selected, and the user can also write his/her own synthesis using code in a special coding window. The nodes can also contain sound samples that are triggered when the node is activated. The piano keyboard view is optional and not graphically connected to the grid itself in any way. It shows the notes played, indicated with grey if the pitch maps to the western 12-tone scale but red if it is a microtone.

The interactive attributes (related to playing) of the instrument consist of a space where one can play scales or notes with the mouse, the Wacom pen or any other interface. There are two types of playing: free playing, where the player can play any note on the grid; and restricted playing, where only the selected notes can be played. That way the instrument can be played as a customly tuned string instrument. Related projects are Spiegel and Hunt [5, 14]. The interface also contains 4 agents that can move through the grid-space, each with its own tempo and step size properties. If the agent lands on a selected node, it triggers the assigned action (playing a synthesised note or triggering a sample). The agents also have a mode where they breed notes (by selecting it) if they mate.