Please download the CHBT manual.


See below, video of the CHBT's first production prototype with Moog® Grandmother:



Welcome to the ALTMANN CHORDERBEAT, the indispensable enabler for your analogue synthesizers.

The CHBT was developed with Moog® Synthesizers in mind (i.e. Grandmother, Little-Phatty, Subsequent, etc.) however can also be used with many standard Synthesizers of other manufacturers or modular Synths.

The ALTMANN CHORDERBEAT comes in a compact, rugged, wearable/mountable package with gold-plated front which holds all operational controls and I/Os. Optional accessories (chained-plug, knobs, velcro, etc.) available upon request.



CHBT receives 12V DC into its power jack and listens to MIDI channel 1 through its 5-pole MIDI input jack.

A red status LED communicates power and MIDI command status.



The Chorderbeat's WAVE output offers 7-note polyphonic square-wave output, which is fine-tuneable, pitch-wheel controlled (via MIDI) and also features AMM's proprietary WARBLE-mode. The WAVE output is typically connected to Filter- or External-Input of your Synthesizer. The 7 internal squarewave oscillators operate with 32-bit resolution and crystal-controlled precision.



The AC-coupled WAVE output's level and distortion is controllable via a volume potentiometer. The first half of the pot range controls volume (level) from zero to app. 9Vpp, the second half of the pot range gradually introduces distortion to the output while maintaining the max output level of 9V peak to peak.



MIDI pitchwheel commands are received by the CHBT and processed to simultaneously modulate the pitch of the 7 internal squarewave oscillators. The pitchwheel amount can be selected between +2/-2 and +2/-12 semi-notes by using the associated DIP-switch.



The Chorderbeat's WAVE-output frequency ranges from app. 2Hz to above 8kHz (16kkHz in DECIMAL-mode).

Dedicated 32" and 16" range can be selectec via DIP-switch.



In TUNE-mode the AMOUNT potentiometer allows for precision tuning in the range of +/-1 seminote. In center position the output wave will be tuned according to A=440Hz. TUNE/WARBLE mode selectable via DIP-switch.



If WARBLE-mode is selected via DIP-switch, and AMOUNT potentiometer is set to zero (fully counterclockwise) the WAVE-output is tuned acc. to A=440Hz.

When AMOUNT pot setting is gradually increased in WARBLE mode and several notes are played simultaneously, notes 1, 4 and 7 will be perfect pitch however notes 2, 3, 5 and 6 will be detuned up/down according to the AMOUNT-pot setting with full detune (1 seminote) achieved at the fully clockwise position. MIDI channel-pressure and aftertouch commands are internally routed to modulate the WARBLE amount.



If DECIMAL-mode is selected via DIP-switch, the octave will be splitted into 10 notes (instead of 12 as in standard mode).

This allows for metric-music compositions, interesting effects or just playing jokes on somebody ;-)

DECIMAL-mode also has 7-note polyphonic WAVE output. Due to its extended frequency-range the octave DIP-switch selection has no effect in DECIMAL-mode.



Mod-wheel, Volume, Aftertouch (Channel-Pressure) and Velocity. All CV-output are DC-coupled 5V.


See below, video of the Altmann Chorderbeat with Moog Subsequent 37 ®:

Moog ® Subsequent with Chorderbeat connected will automatically be polyphonic when FDBK is enabled. This makes it very simple to switch between mono and poly modes. Also in poly mode, the sound becomes very (very) full as the Moogs internal (two) as well as the Chorderbeat's (seven) oscillators are used. As Sub37 and Subsequent 37 ® send Channel-pressure via MIDI, the CHBT's warble mode will be activated automatically if any key of the keyboard is pressed down into after-touch. These go really well together ;-)


See below, video of the Altmann Chorderbeat with Moog Little-Phatty ®:



A limited amount of Chorderbeats is available for ordering @ EUR 795,- incl. shipping to you, please order by email.

EU orders come with 12V power supply. Non-EU orders do not include a power-supply, please purchase a standard 12V DC power supply locally.

Please allow app. 10 .. 14 days for completion.


Please email for questions.

See below, very first CHBT prototype (basic functions only and still on breadboard) with Moog Grandmother:


phone +49-212-233-7039 ... email

Words with ® belong to the Moog company which is in no way affiliated with AMM.