Operating like a touchscreen theremin and fretless guitar neck, the Line Instrument is a controller for performing with your trackpad/mouse/touch surface. As you drag across its screen, continuous pitches are generated as well as a gate signal to control oscillators and envelope generators. The vertical position of your mouse generates cv output too, offering additional expression.
It's surprisingly fun & engaging, encourages you to explore different ideas, and provides an immediacy that makes it easier to tinker with patches. It is a great live tool too.
Each row is a continuous strip of pitches and you can drag across it to produce pitch at the corresponding CV output (1 per row). There's also an "active" output which send the pitch CV signal from whichever row you're using. So, you can either use each row to control a different destination, or use the whole thing as one big controller. A blue button to the left of these outputs can be toggled so that either the rows are distributed to different octaves or they are repeats of the same octave. There's also a transposition dial. The vertical lines represent harmonious relationships, so you can use them as guides for being in tune (kind of like frets) and you can also position your own colorful lines to mark custom pitches (small dials below "pitch cv" label).
The gate outputs are likewise both individual (1 per row) and collected into an "active" output which sends a gate while you're actively dragging on any row. The "vert CV" section outputs a CV signal corresponding to the vertical location, within a row, where you are dragging. These outputs are again both individualized for each row and collected into an "active" output.
You can also drag markers into place on the rows to produce chords. The dial on the bottom left cycles through memory slots of stored positions, so you can use this as a versatile method for cycling through harmonies. There's a neighboring cv range dial and a toggle to switch between responding to a trigger or working from a modulation signal.
All of these controls mean that you can use this device as a highly customizable controller for many purposes, from performing theremin-like melodies to generating expression like a touch surface to storing continuous pitch values for off-kilter harmonies.