There are a variety of Tonal Plexus keyboards to choose from. The table below compares some basic aspects of the available options.

Controller /
Synthesizer		 Model Octaves Keys Synth /
Amp		 Modulation,
Volume,
Velocity
Control		 Envelope
Control*		 EQ
Control*		 Effect &
Param
Control*		 Global
Pitch Bend*
Mode: on / off		 Joystick
Option		 Expansion
Ports		 Price
(USD)
Controller
Only		 TPX2 2 422 no yes yes yes no ± 2 no 0
TPX4 4 844 no yes yes yes no ± 2 no 0
TPX6 6 1266 no yes yes yes no ± 2 no 0
Controller &
Synthesizer		 TPX2s 2 422 yes yes yes yes no ± 2 no 0
TPX4s 4 844 yes yes yes yes no ± 2 no 0
TPX6s 6 1266 yes yes yes yes yes ± 0 - 12 yes 1
TPX8s 8 1688 yes yes yes yes yes ± 0 - 12 yes 3

* these MIDI messages are based on the Roland GS standard and will work with some external Roland synthesizers. Other external synthesizers will ignore these messages or respond in some other way.

Traditional Keyboard Comparison

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Alternative Keyboard Comparison

No other MIDI device does what the Tonal Plexus does. Tonal Plexus TPX keyboards are designed as part of a complete theoretical system based on research in musical tuning and human pitch perception. The keyboards are designed specifically for microtuning with General MIDI compatibility, and the key layout and master tuning are integrated with a microtonal notation system. In other words, what you are getting with a Tonal Plexus keyboard is a complete musical package, and you don't have to understand the details to see and hear why that makes a difference. Some customers have asked how the Tonal Plexus compares to the alternative MIDI devices listed below. The table summarizes some important points of comparison. What's right for you? You decide!

Company Product(s) Layout Octaves Keys per
Octave		 Key Color
Options		 Designed for
Microtuning		 Any Key =
Any Pitch		 Sends Tuned
MIDI Output		 General MIDI
Microtuning1		 Stores
Tuning Tables		 Internal
Synth / Amp		 Velocity Control Price (USD)
H-Pi Instruments Tonal Plexus Hunt 2,4,6,8 211 blue, red
green, yellow 		yes yes yes yes yes (32) optional global (fader / pedal
with adjustable
randomization
bandwidth
per key contact)
Chromatone Chromatone CT-312* Von Janko 8 12** no option no no no no no yes per key (contact) n/a
Cortex Design Terpstra Keyboard* Hex Grid 5 56 no option yes no no no no no per key (Hall effect) $10000
C-Thru Music Axis-64* Hex Grid 5 1/3 12 no option no no no no no no per key (contact) $1700
Haken Audio Continuum Open 4, 8 no keys no option yes no yes yes yes (8) no depth (Hall effect) $3390, $5290
Opal Sonome* Hex Grid 5 1/3 12 custom no no† no no no (42)‡ no per key (contact) £1800
StarrLabs Uath-648*, Uath-990* Hex Grid 4, 7.5 72, 108 no option yes no† no no no (30)‡ optional per key (contact) $3825, $8800
Thumtronics Thummer Wicki 6.5 12 no option no no no no no no per key (n/a) n/a

* H-Pi Instrumets TBX1 can be used with this product to add General MIDI Microtuning1 capability
** this product has hard-wired / mechanically duplicate keys (12-ET output)
† this product allows any key to be assigned to any MIDI Channel and Note, but does not store any tuning information (12ET output)
‡ this product stores MIDI Note Maps (key Note / Channel combination assignments) but does not store any tuning information (12ET output)

1 General MIDI Microtuning refers to the use of a Dynamic Channel Allocation Algorithm for tuning multitimbral synthesizers via pitch bend messages (Patent Application US 11/824,243).