Touch sensitive input for Sonic Pi


Development of a touch sensitive keyboard for use with Sonic Pi, using Adafruit’s MPR121 12 toiuch sensitive input board with OSC support added to the software.

Full article, with link to software is here.

Video of project in action is here.


Sonic Pi 3 Player /Recorder version 1.2

Now released version 1.2 of my Player ?recorder for Sonic Pi 3 utilising a TouchOSC interface. This has expanded considerably since version 1, but as a result is now is not suitable for use on a Pi3. Also, as the program has increased in length it now needs to be run using the run_file command from a text file.(.rb)

Full details of the interface and usage are contained in a page here including a link to the code.

Setting up Sonic-Pi to work with a pisound midi/audio interface board.

I thought it would be useful to gather my experience of using the excellent pisound midi/audio interface board by with Sonic Pi.

The samplerate, frames/period and number of periods/buffer I use in this article give about the lowest latency I have been able to achieve with Sonic Pi on a Raspberry Pi 3. If you are not worried about latency, and mainly using Sonic Pi for playback, you may want to use values which are less demanding, but at the expense of worse latency.
Such figures might be sample rate 48000, frames/period 4096, periods/buffer 3.  I use these when playing pieces that are very demanding of sonic pi, with several parts playing together. Latency for these settings is 256ms as opposed to 21.3ms for the settings used below

Although the pisound board works “out of the box” with Sonic Pi, that is only as far as sound output is concerned. Sonic Pi does not automatically connect the stereo input ports on the pisound board. This is because, by default the Raspberry Pi does not have any audio input ports, and it cannot predict which external cards/boards a user is likely to install.
There are two ways around this problem. The first in non-invasive and makes use of an external program `qjackct` (installed on the Pi) to launch and configure the jackd connector which enables the SuperCollider scsynth which is at the heart of the sounds Sonic Pi produces to talk to the outside world. The second invasive method which involves altering one of the files in Sonic Pi is to configure this file (scsynthexternal.rb) to accommodate the actual board setup (in this case PiSound) that you are using.

In both instances the first thing to do is to set PiSound as the default audio board. This is achieved by using the Audio Device Settings in Preferences on the main Sonic Pi menu. From the Sound Card popup menu select pisound (Alsa mixer) and set it as default, using the Make Default button.

For the non-invasive approach, first open a terminal window and type
killall jackd
qjackctl &
The qjackctl interace window will open up

CLick the Setup Button, then select the Settings Tab and within that the Parameters tab
adjust the parameters as follows:

Driver alsa
Realtime (ticked)
Sample Rate: 96000
Frames/Period: 1024
Periods/Buffer: 2
MIDI Driver: seq

Switch to the Advanced tab and adjust as follows:

Preset Name: (default)
Server Prefix: jackd
Port Maximum: 1024
Time (msec): 500
Audio: Duplex
Dither: None
Output Device: hw:pisound
Input Device: hw:pisound,0
Channels I/0 (both) 2
Latency I/O (default)
Startup Delay: 2 secs
Now click `OK`
Click the `Start` button on the Jackd screen. All being well jackd will start running and the Stop button will show a bright red rectangle beside it.

Click the `Messages` button and select the `Status` tab
You should see values reflecting the Sample Rate 96000 Hz and the Buffer Size 1024 that we set earlier.
Leave qjackctl running and start Sonic Pi
When it has started, you should be able to hear sound from Sonic Pi as usual. Check using for example `play 72`
However you still have to connect the inputs to SuperCollider to use the PiSound input. To do this go back to the qjackctl interface and click on the Connect button.
You should see two entries on the left pane, `SuperCollider` and `system` and two entries on the right pane `SuperCollider` and `system`

These represent the output and input ports. You will see that the Supercollider output is connected to the system input, enabling aduio to go from Sonic Pi to your audio sysetm where you can hear it.
However the input to SuperCollider on the right hand side is disconnected. Use your mouse to drag a connection line diagonally from the system output (your microphone for example) to the SuperCollider input
Note you can expand each of these which makes it a bit clearer. You will see the two system capture ports connected to the two “in” ports in SuperCollider.

If you now connect an audio source to the PiSound board eg a guitar or microphone, you can run the program below to test it.

with_fx :compressor,amp: 4 do
live_audio :min # for a mono input

For a stereo input change the live_audio line to `live_audio :min,stereo: true`

The invasive method.

Using qjackctl is easy and it allows you to experiment with different settings for the sample rate, buffer size (frames/period) and number of periods/buffer. By default Sonic Pi uses 41000Hz for the sample rate, 2048 frames/period and 3 periods/buffer which is more conservative to suit the inbuilt audio card, but which gives a much larger latency. recommend that you only use 48000, 96000 and 192000 with pisound, otherwise it has to do resampling. 192000 is a bit too high for Sonic Pi so try the other two.
If you want to dispense with qjackctl you can alter one of the files in Sonic Pi, but you should only attempt this if you know what you are doing and are comfortable with hacking apps.

The file in question is named scsynthexternal.rb and it is a Ruby text file situated inside the app. The following changes apply to the current release version on Raspberry Pi which is 3.0.1
If you have installed Sonic Pi using apt-get install or are using an up to date raspbian stretch you will find the file at:


It is saved as user root, so you have to access it using sudo. In a terminal type:

sudo leafpad

When the text editor opens navigate to the file listed above and open it.
First save a backup copy of the file. eg save as scsynthexternal.rb.backup
Then reopen the original and scroll to line 363 and 364 which show

# `jack_connect SuperCollider:in_1 system_capture_1`
# `jack_connect SuperCollider:in_2 system_capture_2`

alter these to read as follows:

`jack_connect SuperCollider:in_1 system:capture_1`
`jack_connect SuperCollider:in_2 system:capture_2`

Note there are TWO changes on each line
Then scroll to line 350 which reads:

jack_pid = spawn "jackd -R -p 32 -d alsa -d hw:#{audio_card} -n 3 -p 2048 -o2 -r 44100& "

put a # before the line to comment it out, and add an extra line below it.

#jack_pid = spawn "jackd -R -p 32 -d alsa -d hw:#{audio_card} -n 3 -p 2048 -o2 -r 44100& "
jack_pid = spawn "jackd -R -p 32 -d alsa -d hw:#(audio_card) -n 2 -p 1024 -o2 -i2 -r 96000& "

(note this will alter subsequent line numbers by 1 if you scroll back to the first change)

Save the file, replacing the original.
Exit the text editor, and try running Sonic Pi (without using qjackctl first)
All being well it will startup and you should be able to run the live_audio example.

One final point. You can’t use the volume slider on the Raspberry Pi Menu Bar with the PiSound board. Instead use the volume knob on the PiSound itself.

Problems. If you find Sonic Pi won’t start and that it times out with an error message, this can sometimes be because parts of the app are left running and interfere with subsequent attempts to start it. One drastic cure for this is to restart the Raspberry Pi. Alternatively you can open a terminal window and issue a series of commands to kill these sub programs.

You can try:

ls -ae

and look for any entries that contain sonic-pi, ruby, scsynth, jackd, m20 or o2m
if so try

killall sonic-pi
killall ruby
killall scysnth
killall jackd
killall m2o
killall o2m

You may get no process found responses, which is fine, but for any that you don’t get this then you have successfully stopped the offending app.
Now try restarting Sonic Pi.

I hope that this article will be useful to you if you have a pisound. You can also find help in the pisound community section at

A visualiser for Sonic Pi 3

Every since Sonic PI had a transparency mode added (not available on the Raspberry Pi versions) I have been interested in adding a Visualiser graphics display as a backdrop. The built in Scope can give attractive displays, but I wanted something with a bit more colour, and which covered the whole screen. I did some experiments with the iTunes visualiser which added quite a nice backdrop, but only with a significant delay between the audio and the fluctuations of the display. The recent arrival of Sonic Pi 3 allowed for further possibilities, because it enabled the use of OSC messaging. I did a trawl of the internet and came across a promising looking processing sketch which produced a pattern which reacted to incoming audio. It was written several years ago and was only monochrome based. I played around with this, upgrading it to work on the latest version of Processing, and added some colour. I experimented with adding further  basic shapes to the display (it originally used an ellipse primitive, set up to give concentric circles, which could also be driven to produce a star burst effect). I added rectangles and star shapes and experimented with off-setting these as the program ran, and also with using more than one basic shape at the same time. I then added some code so that the sketch could receive incoming OSC messages sent from Sonic Pi 3, which could be used to control various parameters for the shapes, such as stroke width, colour, and offsets on the screen. I added further flexibility such as the ability to rotate the shapes, and to shift the whole display vertically and horizontally across the screen. The final setup works well with Sonic Pi 3, which controls the patterns both with the Audio signal it produces, and also with OSC messages which can be sent to the sketch display code. These can be timed appropriately with the musical content.

The code for the sketch is shown below

//Visualiser for use with Sonic Pi 3 written by Robin Newman, September 2017
// based on an original sketch
//Changes: changed to full screen, updated for Processing 3, added colour, added rectangle and star shapes
//added OSC input (from Sonic Pi) to alter parameters as it runs, removed slider inputs.
//input OSC:   /viz/float       updates STROKE_MAX, STROKE_MIN and audioThresh
//             /viz/pos         updates XY random offset values (can be zero)
//             /viz/col         updates RGB values
//             /viz/shapes      sets shapes to be used from S, E and R (or combinations thereof)
//             /viz/stardata    sets data for star shapes
//             /viz/rotval      turns rotation of shapes on/off
//             /viz/shift       turns XY shift across screen on/off
//             /viz/stop        initiates sending stop all signal back to Sonic Pi port 4557

import ddf.minim.analysis.FFT;
import ddf.minim.*;
import oscP5.*; //to support OSC server
import netP5.*;

Minim minim;
AudioInput input;
FFT fftLog;

int recvPort = 5000; //can change to whatever is convenient. Match with use_osc comand in Sonic Pi
OscP5 oscP5;
NetAddress myRemoteLocation; //used to send stop command b ack to Sonic PI

// Setup params
color bgColor = color(0, 0, 0);

// Modifiable parameters
float STROKE_MAX = 10;
float STROKE_MIN = 2;
float audioThresh = .9;
float[] circles = new float[29];
float DECAY_RATE = 2;
//variables for OSC input
float [] fvalues = new float[5]; //STROKE_MAX, STROKE_MIN,audioThresh values
int [] cols = new int[3]; //r,g,b colours
int [] positions = new int[2];// random offset scales for X,Y
int [] stardata = new int[4];// data for star shape, number of points, random variation
int shiftflag = 0; //flag to control xy drift across the screen set by OSC message
int two = 0; //variable to force concentric shapes when more than one is displayed
String shapes = "E"; //shapes to be displayed, including multiples from S,E,R
int rotval =0;
int xoffset = 0,yoffset = 0;
int xdirflag = 1,ydirflag = 1;

void settings() {

void setup() {  
   myRemoteLocation = new NetAddress("",4557); //address to send commands to Sonic Pi
  minim = new Minim(this);
  input = minim.getLineIn(Minim.MONO, 2048); //nb static field MONO referenced from class not instance hence Minim not minim

  fftLog = new FFT( input.bufferSize(), input.sampleRate()); //setup logarithmic fast fourier transform
  fftLog.logAverages( 22, 3); // see

  ellipseMode(RADIUS); //first two coords centre,3&4 width/2 and height/2
  cols[0] = 255;
  positions[0] = 50;
  /* start oscP5, listening for incoming messages at recvPort */
  oscP5 = new OscP5(this, recvPort);

void draw() {
  //calculate changing xy offsets: shiftflag set to 0 to siwtch this off
  xoffset += 10*xdirflag*shiftflag;
  yoffset += 10*ydirflag*shiftflag;
  if(shiftflag==0){xoffset=0;yoffset=0;} //reset offset values to zero if shifting is off
  //reverse directions of shifting when limits reached
  if (xoffset >displayWidth/3){xdirflag=-1;}
  if (xoffset < -displayWidth/3){xdirflag=1;} if (yoffset > displayHeight/3){ydirflag=-1;}
  if (yoffset < -displayHeight/3){ydirflag=1;}
  //transform to new shift settings
  translate(displayWidth/2+xoffset, displayHeight/2+yoffset); //half of screen width and height (ie centre) plus shift values

  //optional rotate set by OSC call
  //get limits for stroke values and audiThreshold from OSC data received
  //println("fvalues: ",STROKE_MIN,STROKE_MAX,audioThresh); //for debugging

  // Push new audio samples to the FFT

  // Loop through frequencies and compute width for current shape stroke widths, and amplitude for size
  for (int i = 0; i < 29; i++) {

    // What is the average height in relation to the screen height?
    float amplitude = fftLog.getAvg(i);

    // If we hit a threshold, then set the "circle" radius to new value (originally circles, but applies to other shapes used)
    if (amplitude < audioThresh) { circles[i] = amplitude*(displayHeight/2); } else { // Otherwise, decay slowly circles[i] = max(0, min(displayHeight, circles[i]-DECAY_RATE)); } pushStyle(); // Set colour and opacity for this shape circle. (opacity depneds on amplitude) if (1>random(2)) {
      stroke(cols[0], cols[1], cols[2], amplitude*255);
    } else {
      stroke(cols[1], cols[2], cols[0], amplitude*255);
    strokeWeight(map(amplitude, 0, 1, STROKE_MIN, STROKE_MAX)); //weight stroke according to amplitude value

    if (shapes.length()>1) { //if more than one shape being drawn, set two to 0 to draw them concentrically
      two = 0;
    } else {
      two = 1;
    // draw current shapes
    if (shapes.contains("e")) {
      // Draw an ellipse for this frequency
      ellipse(random(-1, 1)*amplitude*positions[0]*two, random(-1, 1)*amplitude*positions[1]*two, 1.4*circles[i], circles[i]);
    if (shapes.contains("r")) {
      rect( random(-1, 1)*amplitude*positions[0]*two, random(-1, 1)*amplitude*positions[1]*two, 1.4*circles[i], circles[i]);
    if (shapes.contains("s")) {
      strokeWeight(3); //use fixed stroke weight when drawing stars
      //star data Xcentre,Ycentre,radius1,radius2,number of points
      star(random(-1, 1)*amplitude*positions[0]*two, random(-1, 1)*amplitude*positions[1]*two, circles[i]*stardata[0], circles[i]/stardata[1], int(stardata[2]+random(stardata[3])));

    //System.out.println( i+" "+circles[i]); //for debugging
  } //end of for loop

void oscEvent(OscMessage msg) { //function to receive and parse OSC messages
  System.out.println("### got a message " + msg);
  System.out.println( msg);
  System.out.println( msg.typetag().length());

  if (msg.checkAddrPattern("/viz/float")==true) {
    for (int i =0; i<msg.typetag().length(); i++) {
      fvalues[i] = msg.get(i).floatValue();
      System.out.print("float number " + i + ": " + msg.get(i).floatValue() + "\n");

  if (msg.checkAddrPattern("/viz/pos")==true) {
    for (int i =0; i<msg.typetag().length(); i++) {
      positions[i] = msg.get(i).intValue();
      System.out.print("pos number " + i + ": " + msg.get(i).intValue() + "\n");

  if (msg.checkAddrPattern("/viz/col")==true) {
    for (int i =0; i<msg.typetag().length(); i++) {
      cols[i] = msg.get(i).intValue();
      System.out.print("col number " + i + ": " + msg.get(i).intValue() + "\n");
  if (msg.checkAddrPattern("/viz/shapes")==true) {
    //for(int i =0; i<msg.typetag().length(); i++) {
    // shapes += msg.get(i).stringValue().toLowercase();      
    System.out.print("shapes code "+ shapes + "\n");
  if (msg.checkAddrPattern("/viz/stardata")==true) {
    for (int i =0; i<msg.typetag().length(); i++) {
      stardata[i] = msg.get(i).intValue();
      System.out.print("stardata number " + i + ": " + msg.get(i).intValue() + "\n");
  if (msg.checkAddrPattern("/viz/rotval")==true) {
    rotval =msg.get(0).intValue();
    System.out.print("rotval code "+ rotval + "\n");
  if (msg.checkAddrPattern("/viz/shift")==true) {
    shiftflag =msg.get(0).intValue();
    System.out.print("shiftflag code "+ shiftflag + "\n");
  if (msg.checkAddrPattern("/viz/stop")==true) {
    kill(); //stop Sonic Pi from running

//function to draw a star (and polygons)
void star(float x, float y, float radius1, float radius2, int npoints) {
  float angle = TWO_PI / npoints;
  float halfAngle = angle/2.0;
  for (float a = 0; a < TWO_PI; a += angle) {
    float sx = x + cos(a) * radius2;
    float sy = y + sin(a) * radius2;
    vertex(sx, sy);
    sx = x + cos(a+halfAngle) * radius1;
    sy = y + sin(a+halfAngle) * radius1;
    vertex(sx, sy);

void kill(){ //function to send stop message to Sonic Pi on local machine
  OscMessage myMessage = new OscMessage("/stop-all-jobs");
   myMessage.add("RBN_GUID"); //any value here. Need guid to make Sonic PI accept command
  oscP5.send(myMessage, myRemoteLocation); 

The basis of a visualiser depends on doing a fast fourier transform analysis of the incoming audio, and calculating amplitudes related to the different frequency components of the audio, which is continuously monitored input buffer by input buffer. I don’t intend togo anywhere near the complex mathematics involved, but there are a lot of useful articles at different levels which you can read on the subject. I quite liked this one on the Fourier Transform. Also it is useful to look at the documentation of the minim library analysis section if you want more detailed information on the calls employed.
You may find it easier to look at the original sketch from which I started before taking on board the additions I have added to make the sketch more flexible and wide ranging.
I have added various transformations. Starting at the beginning of the main draw() function there are x and y offsets which increase each time the loop iterates, until a maximum offset is reached, when they reverse in direction. This causes the shapes to move smoothly left and right and up and down the screen. a shiftflag eanbles this to be siwtched on and off by one of the control OSC messages.
There follows an optional rotate command which can rotate the axis of the shapes being drawn, again controlled by an incoming OSC message.
Next values for setting the limits on the stroke size being used to render the shapes are read from data received by an OSC message, together with an audioThreshold setting.
A buffer from the input audio is now processed, and amplitude values for different frequency ranges are stored in an array of “circle” settings. NB the name circles is used for the variable as this was the only shape used in the original.Perhaps it might be better names shapes() now as there are three different classes of shapes used. A new value for the “radius” is stored if it is less than the audioThreshold setting, otherwise, a “decayed” value of the currently stored value from the previous iteration is stored. (suitable minimum values are set).
rgb colour values are set using values received from an OSC message, and these are then swapped at random, before setting the stroke colour attributes  to be used.
Next a flag two is set according to whether  one or more than one shapes have been selected. In the latter case the shapes are forced to be drawn concentrically, by nullifying the offset values by setting two = 0. The selected shapes are then drawn, before the loop starts a further iteration.

The oscEvent(OscMessage msg) function is triggered when an OSC message is received. It contains sections to parse the various OSC messages which can be sent from Sonic PI to the processing sketch. The parameters for each command are used to update various lists containing information used by the draw cols[ ] holds rgb values, startdata[ ] holds the parameters for the star shapes, fvalues[ ] holds the floating point values for the STROKE_MAX, STROKE_MIN  and audioThresh settings. These and other similar settings are updated when the relevant OSC messages are received, so Sonic PI can control the operation of the sketch as it runs.
The star functions draws the star shape. It is lifted straight from the star example here
The final function kill( ) is used to send a /stop-all-jobs OSC message back to Sonic PI to stop all programs running on that machine. It can be triggered by a /viz/stop OSC message being sent from Sonic PI to the Sketch.

As far as Sonic Pi is concerned, it produces two sorts of input. First the audio that it produces is fed back to the sketch which looks at the default audio input. On my Mac I used the program Loopback ( ) to perform this. This is a paid for program, but you can use it for free for 10 minutes or so at a time.It is based on the previous free SoundFlower utility, but this has not been fully updated for recent MacOS and you may find it difficult to get it to work instead. The setup I used is shown below:Note that Sonic Pi is added as a Source and that its output is monitored through the speakers, so that the audio is fed both there and to the processing sketch. This loopbackdevice will appear in the list of devices in the MIDI audio setup program, and should be selected as the default input device,

Secondly, Sonic PI is used to send OSC messages to the processing sketch to control its various parameters. this can be done by sending “one off” messages or by putting the message sender into a live loop, sending messages at regular intervals. An example is shown below, where the OSC messages are combined with the program producing the music, but they can  be run as a separate program in a different buffer, which is an advantage if you are visualising a linear piece and do not want to restart it every time you press run to update the OSC messages sent.

#Program to drive Sonic Pi 3 visualiser written in "processing"
#by Robin Newman, September 2017
#see article at
#set up OSC address of processing sketch
use_osc '',5000
#select shapes to show
osc "/viz/shapes","e"  #"s" "e" "r" Star,Ellipse, Rectangle or combination
sleep 0.1

live_loop :c do
  #choose starting colour for shapes
  osc "/viz/col",rrand_i(0,64),rrand_i(128,255),rrand_i(0,255)
  sleep 0.1

live_loop :f do
  #set Stroke max min widths and audioThreshold
  osc "/viz/float",([8.0,5.0,3.0].choose),[1.0,2.0].choose,(0.4+rand(0.3))
  sleep 2

#set range of random positional offset (can be 0,0)
#automatically disabled when showng more than one shape
osc "/viz/pos",20,0

#control "bouncing" shapes around the screen 1 for on 0 for off
osc "/viz/shift",0

live_loop :s do
  #setup star data inner/outer circle radius, number of points
  #and random variation of number of points
  osc "/viz/stardata",[1,2].choose,[1,2,3].choose,5,2
  sleep 4

rv=0 #variable for current rotation
live_loop :r do
  rv+=5*[-8,1].choose # choose rotation increment
  osc "/viz/rotval",rv #change rv to 0 to disable rotation
  sleep 0.1

#Now setup the sounds to play which will trigger the visualiser
use_bpm 60
set_volume! 5
use_random_seed 999

with_fx :level do |v|
  control v,amp: 0 #control the volume using fx :level
  sleep 0.1
  in_thread do #this loop does the volume control
    control v,amp: 1,amp_slide: 10 #fade in
    sleep 140
    control v,amp: 0,amp_slide: 10 #fade out
    sleep 10
    osc "/viz/stop" #send /viz/stop OSC message to sketch
    #sketch sends back a /stop_all_jobs command to port 4557
  #This drum loop is written by Eli see!topic/sonic-pi/u71MnHnmkVY
  #used with his permission. I liked it, and it has good percussive output
  #to drive a visualiser
  live_loop :drums do
    this_sample = [:loop_compus, :loop_tabla, :loop_safari].ring
    start = [ 0.0 , 0.125 , 0.25 , 0.375 , 0.5 , 0.625 , 0.75 , 0.875 ].ring
    sample this_sample.look , beat_stretch: 4, start: start.look, rate: 0.5
    sleep 1

As this program runs, you can alter the parameters eg shape(s) chosen, shift parameter etc. and rerun. Effectively live coding the visualiser. The program uses a great percussion loop written by Eli, which he said I might use.!topic/sonic-pi/u71MnHnmkVY

There is a video of the program in operation on youtube here

and you can download the code for the sketch and Sonic Pi programs here

You can download and install Processing from

You will also have to install the libraries Minim and oscP5 from the Sketch=>Import Library… menu.
To use, set up the loopback audio and select it as the default input device. Load and play the sketch in processing, then run the Sonic Pi program on the same computer. You can adjust the transparency of the Sonic Pi screen on the Preferences Visuals tab to make it semi transparent, or minimise Sonic Pi once it is running, if you are not going to do live coding of the control OSC messages.