LinnStrument is part of a class of instruments that I (Roger) believe is the next revolution in electronic music performance: MPE instruments, musical performance controllers that capture three dimensions of finger movement, polyphonically. These instruments stand in sharp contrast to the standard MIDI keyboard, which consists of little more than on/off switches, albeit with velocity sensing, monophonic pressure sensing for the last 5% of the key's travel, and two sideways knobs to create unnatural-sounding pitch bends and mathematically-perfect vibratos.
In addition to LinnStrument, there are the following MPE instruments that are of high quality with continuous 3D sensing + velocity, and a wide enough pitch range suitable for professional performance. They are presented below in alphabetical order.
The Continuum from Haken Audio consists a soft playing surface with a fabric top layer (similar to a mouse pad) in which the notes are arranged as a long continuous strip of evenly-spaced semitones. Each finger's pressure (expression), left/right position (pitch) and forward/backward position (timbre) is continuously sensed, and all fingers are sensed polyphonically. It also includes integrated highly-expressive sound synthesis for this three-dimensional finger gesture capture. Here are some videos: bowed-string sound, Gabriel's Continuum, lap steel, flute-like sound, plucked string sound, muted trombone sound. Note: the Continuum was first released in 1999--well before any of the others--and is a clear statement of the innovative thinking of its designer Lippold Haken.
The Eigenharp is not only an excellent collection of ideas but also a very beautifully hand-crafted instrument. Its main keyboard consists of 120 keys arranged as 5 columns of 24 keys each, and each key is sensitive to simultaneous pressure, forward-backward tilt and left-right tilt, simultaneously and polyphonically, all sampled at 2000 Hz and with 10-bit resolution (1024 levels). The rows can be configured as chromatics, major, minor or one of a large number of other scales, and the pitch offset between rows can be set to any interval you like. It also has two strip controllers, a wind controller, and 12 additional keys for percussion, bowing or strumming. They also make a lower-cost version called the Tau, as well as a very low-cost version called the Pico. Here are some videos: overview, acoustic guitar. The Eigenharp was designed primarily by the company's founder John Lambert.
The Joué looks like a mini-LinnStrument and has the same general function, to respond to three dimensions of touch, polyphonically. But unlike LinnStrument, its touch surface is a fully free-form pressure-sensitive multi-touch surface, permitting any touch to be tracked from any position to any other position. And it comes with a variety of overlays for different note arrangements-- piano, guitar/grid, drum pads and more. Though the playing surface is small and therefore has limited pitch range, it delivers a very good value for its low price of 479.00€ including 5 overlays. Joué was developed by a very creative team led by Pascal Joguet, who is the creator of the JazzMutant Lemur.
The K-board Pro 4 by Keith McMillen Instruments, makers of other expressive control surfaces, is the closest MPE controller to the feel of a traditional piano keyboard, with separate keys and raised black keys. It responds to pressure, left-right and forward-backward movements on the keys, polyphonically. Though it does not permit sliding in pitch from one note to another, I suspect many pianists will find this limitation insignificant compared to the value of the familiar piano interface.
The SeaBoard Rise from Roli Labs uses a soft rubber playing surface molded into a shape similar to a piano keyboard. Finger movements on this surface are sensed in three dimensions-- pressure for expression, left/right for pitch and forward/backward for timbre-- independently for each simultaneous finger touch. For keyboard players, this provides the advantage of expressive polyphonic control in a familiar note layout. Click the link above for a video of this innovative instrument in performance. This instrument was designed primarily by the company's founder, Roland Lamb.
The SoundPlane from Randy Jones' Madrona Labs is 3D-sensing multi-touch surface that samples 1000 times per second at 12 bit resolution. It also is hand-crafted from fine woods and finishes, in keeping with the fine musical instrument it is. Also, there are two things I (Roger) like about the SoundPlane: 1) SoundPlane is a completely free-form touch surface, meaning that a touch can be tracked from anywhere to anywhere else on the surface. By comparison, LinnStrument's Y-axis range is limited to the 3/4" height of each row, and cannot be tracked continuously from one row to another. 2) The wood playing surface is divided into note regions consisting of a vertical rectangle. Compared to LinnStrument's 3/4" square note regions, this provides a longer and more usable Y-axis range.