Author: Israel Reyes Rodríguez (isRasta)
Contact: amiga68k@gmail.com
This library attempts to simulate a Hammond B3 organ and a Leslie speaker with two cabinets (Drum & horn). Unlike other organ simulators, the tones are generated from a sinus wave calculated at the start of the performance. The code only uses integers except in the calculation of the musical note. This is so that it works on CPUs without a floating point unit. Electuno has a lot of glitches and unwanted noise, but by using some capacitors and resistors at the output of the DAC, it can sound similar to a Hammond organ. You can hear it in the sample video.
I will try to make all my work open source; If someone wants to motivate me to continue making inventions, they can help me in many ways: Giving me a like, sharing these projects, helping with programming, improving electronic schematics, or with a subscription to my patreon; There is free and there is also payment: https://www.patreon.com/isRasta
Demo video: https://youtu.be/f7KLLlDKEW8?si=Gs59R1dpGhj4l2iC
Jammond (Electuno inside) demo video:https://youtu.be/EwPbPl_iizA?si=TqNFOTpDPPFFmA4X
Bug & problems
Unwanted distortion when all drawbars are open and the expression pedal is maxed out. (A temporary solution is to change OUTBITSHIFT 3 to 4)
The scanner vibrato effect introduces some distortion.
The rotary effect code generates a lot of noise, especially in the high-pass filter; I have tried raising the output frequency to 32Khz but it doesn't improve anything. I have to find a way to create a filter as fast as the current one but with less loss of quality. At the moment I don't have a solution for this, but it improves a lot if we don't use the high-pass filter at its maximum value. It is also quite disguised by adding a physical low-pass filter by adding a suitable capacitor between the sound output and the ground signal.
There are more problems, but I hope I can solve them.
Any suggestion or help is appreciated.
Requirements:
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Tested on different cards and architectures: Arduino NANO, UNO, MEGA (8 bits) and DUE (32 bits). ESP8266 and ESP32 also working (See example files).
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MCP4921 12 bits DAC. (Optional, but example code has writen for this).
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Midi library. Get from Arduino library manager or from https://github.com/FortySevenEffects/arduino_midi_library.
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MCP_DAC library. Get from Arduino library manager or from https://github.com/RobTillaart/MCP_DAC.
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Arduino Due: Needs DueTimer library from Arduinolibrary manager or get from: https://github.com/ivanseidel/DueTimer.
Changes in this version:
- Added MIDI control for pseudorealtime tuning.
- Update example code for MCP_DAC library compatibility.
Specifications:
- Sound output through DAC MCP4921 (It is possible to operate it through PWM or other DACs).
- Controllable via MIDI (You need the MIDI library from the Arduino repositories).
- Fully modular to be able to disable functions on low-power CPUs.
- Simulates two independent keyboards and pedal, with nine drawbars each.
- Foldback effect on last 2 octaves.
- Percussion effect on the upper keyboard.
- Independent vibrato chorus scanner effect for each keyboard.
- Delay effect to simulate a reverb.
- Overdrive effect.
- Two-way Leslie speaker with different speeds and accelerations.
Only tested with Arduino IDE 1.8.19.
Arduino NANO/UNO/MEGA
To use this library on an 8-bit AVR, it is necessary to define LOWRAM. In this mode the polyphony is limited to 8, and it is only capable of simulating one way of the rotary effect. Because of this, the sound is more similar to a Yamaha Electone organ with its built-in rotary speaker.
ESP8266 and ESP32 notes
First you must install support for this MCU in Arduino IDE:
ESP8266: https://www.google.com/search?q=esp8266+on+arduino+ide
ESP32: https://www.google.com/search?q=esp32+on+arduino+ide
Once support for your board is installed, you must install this library from the Arduino library manager; Just search for 'electuno' and the available versions will appear. Inside Arduino IDE, go to the menu 'file->examples->electuno->ESP8266xxxxxx'. Choose the type of board in the 'Tools' menu. Choose the maximum CPU speed.
See schematics for ESP8266: https://github.com/amiga68k/electuno/blob/main/extras/electuno_schematics_nodeMCU.png
Pin configuration for ESP32 and MCP4921:
ESP32 MCP4921
GPIO23 -> SDI(pin4)
GPIO18 -> SCK(pin3)
GPIO15 -> CS(pin2)
COMPILATION OPTIONS:
LOWRAM
Forces setting of main variables to 8 bits and select fixed 8 popyphony tonegenerator. Avaiable options:
Disable by default. No value is required, only write:
- #define LOWRAM
WAVEMIXMODE
Affects the volume of the drawbars in certain parts of the keyboard. Avaiable options:
- 0 = All drawbars and tones have same volume.
- 1 = Some tones have atenuation like analog organs. -Default-
FREQTUNE
Used to multiply the base number by which the frequencies of musical notes are generated. Avaiable options:
- x = Float number. 1 is for 44100Hz output frequency. 2 for 22050Hz... Etc.
- 2 = For a 22050Hz output. -Default-
VOLUMECONTROL
Turns the independent upper/lower/pedal volume control on or off. Avaiable options:
- 0 = Disable. -Default-
- 1 = Enable.
- 2 = Enable with fix for 8 bit microcontrollers as 328P.
EXPRESSIONPEDAL
Set up the expression pedal. Avaiable options:
- 0 = Disable. -Default-
- 1 = Enable
WAVESIZE
Configures the size in bits of the sine wave and the arrays that contain the mix samples. Theoretically, more is better, but it consumes more memory.Avaiable options:
- 7 = 7 bits wave size ( Only tested from 7 to 12 ). -Default-
POLYPHONY
- Configures the polyphony. Avaiable options:
- 8 = 8 note polyphony of 16(max). -Default-
UPPERMODE
Defines the operation of the upper keyboard. Avaiable options:
- 0 = Disable upper keyboard
- 1 = Enable only flutes, without percusive harmonics -Default-
- 2 = Enable flutes and percusive keys harmonics
LOWERMODE
Defines the operation of the lower keyboard. Avaiable options:
- 0 = Disable lower keyboard. -Default-
- 1 = Enable only fors four flutes harmonics.
- 2 = Enable all flutes harmonics.
PEDALMODE
Defines the operation of the pedal bass keyboard. Avaiable options:
- 0 = Disable bass pedal. -Default-
- 1 = Enable with separated dry audio bus as Yamaha Electone style organs
- 2 = Enable with upper/lower mixed audio bus. Overdrive, reverb and rotary affects in this mode
CHORUS
Defines the operation of the pedal bass keyboard. Avaiable options:
- 0 = Disable chorus vibrato effect. -Default-
- 1 = Enable with mixed bus for upper/lower
- 2 = Enable with an independent audio bus for each keyboard
CHORUSBUFFERSIZE
Sets the buffer size for the chorus effect, in bits. ATTENTION: The size of the buffer for this effect directly affects the tuning of the vibrato effect; For this reason there is no real default value, as it depends on the output frequency. Avaiable options:
- 4 = 16 steps vibrato effect. -Default-
REVERB
Enable or disable reverb effect. Avaiable options:
- 0 = Disable- -Default-
- 1 = Enable reverb effect.
OVERDRIVE
Enable or disable overdrive effect. Avaiable options:
- 0 = Disable. -Default-
- 1 = Enable overdrive effect.
LESLIE
Sets the rotary effect on or off. Avaiable options:
- 0 = Disable. -Default-
- 1 = Enable but only one rotor simulation, same as spinet organs internal rotary speaker.
- 2 = Enable with two bus of audio for drum/horn speakers, try to simulate external leslie cabinets.
LESLIEBUFFERSIZE
Sets the buffer size for the rotary effect, in bits. ATTENTION: The size of the buffer for this effect directly affects the tuning pitch and filters of the rotary effect. Avaiable options:
- 7 = 7 bit rotary effect buffer. -Default-
- Only tested ...7,8,9,10,11. For more than 11 bits, a more powerful CPU is needed.
Default MIDI configuration
Channel 1 (Upper & effects control):
- 3 Upper volume
- 11 Expression
- 50 Lower vibrato switch
- 51 Upper vibrato switch
- 54 Overdrive
- 55 Rotary off/slow/fast
- 56 Rotary drum vibrato amount
- 57 Rotary horn vibrato amount
- 58 Rotary lowpass filter
- 59 Rotary hipass filter
- 80 Enable percusive keys
- 81 Percusive key harmonic (4' & 2'2/3)
- 82 Percusive key decay time (slow & fast )
- 70 Drawbar 16'
- 71 Drawbar 5'1/3
- 72 Drawbar 8'
- 73 Drawbar 4'
- 74 Drawbar 2'2/3
- 75 Drawbar 2'
- 76 Drawbar 1'3/5
- 77 Drawbar 1'1/3
- 78 Drawbar 1'
- 91 Reverb control
- 94 Tune frequency (No realtime, only change on new played keys)
Channel 2 (Lower):
- 3 Lower volume
- 70 Drawbar 16'
- 71 Drawbar 5'1/3
- 72 Drawbar 8'
- 73 Drawbar 4'
- 74 Drawbar 2'2/3
- 75 Drawbar 2'
- 76 Drawbar 1'3/5
- 77 Drawbar 1'1/3
- 78 Drawbar 1'
- 91 Reverb
Channel 3 (Pedals):
- 3 Pedal volume
- 70 Drawbar 16'
- 71 Drawbar 5'1/3
- 72 Drawbar 8'
- 73 Drawbar 4'
- 74 Drawbar 2'2/3
- 75 Drawbar 2'
- 76 Drawbar 1'3/5
- 77 Drawbar 1'1/3
- 78 Drawbar 1'
Schematics
R4 and C1 must be adjusted to achieve a suitable sound filter according to the output frequency.
Arduino Nano Scheme
NodeMCU esp8266 Scheme
