Using a Raspberry Pi as a piano

Recently I posted about my successful attempt to get LinuxSampler running on the Raspberry Pi. I’ve taken this a bit further and produced a script that turns the Raspberry Pi into a fully fledged piano. Don’t expect miracles, the sample library I used is good quality so the RPi might choke on it every now and then with regard to disk IO. But it’s usable if you don’t play too many notes at once or make extensive use of a sustain pedal. I’ve tested the script with a Class 4 SD though so a faster SD card could improve stability.

Edit: finally got around buying a better SD card and the difference is huge! I bought a SanDisk Extreme Class 10 SD card and with this SD card I can run LinuxSampler at lower latencies and I can play more notes at once.

Before you can run the script on your Raspberry Pi you will need to tweak your Raspbian installation so you can do low latency audio. How to achieve this is all described in the Raspberry Pi wiki article I’ve put up on After you’ve set up your RPi you will need to install JACK and LinuxSampler with sudo apt-get install jackd1 linuxsampler. Next step is to get the Salamander Grand Piano sample pack on your RPi:

mkdir LinuxSampler
cd LinuxSampler
wget -c
wget -c
tar jxvf SalamanderGrandPianoV2/SalamanderGrandPianoV2_44.1khz16bit.tar.bz2
tar jxvf sgp44.1khz_V2toV3.tar.bz2 -C SalamanderGrandPianoV2_44.1khz16bit

Please note that decompressing the tarballs on the RPi could take some time. Now that you’ve set up the Salamander Grand Piano sample library you can download the script and the LinuxSampler config file:

mkdir bin
wget -c -O /home/pi/bin/piano
chmod +x bin/piano
wget -c
/SalamanderGrandPianoV3.lscp -O

Almost there. We’ve installed the necessary software and downloaded the sample library, LinuxSampler config and piano script. Now we need to dot the i’s and cross the t’s because the script assumes some defaults that might be different in your setup. Let’s dissect the script:


if ! pidof jackd &> /dev/null
  sudo killall ifplugd &> /dev/null
  sudo killall dhclient-bin &> /dev/null
  sudo service ntp stop &> /dev/null
  sudo service triggerhappy stop &> /dev/null
  sudo service ifplugd stop &> /dev/null
  sudo service dbus stop &> /dev/null
  sudo killall console-kit-daemon &> /dev/null
  sudo killall polkitd &> /dev/null
  killall gvfsd &> /dev/null
  killall dbus-daemon &> /dev/null
  killall dbus-launch &> /dev/null
  sudo mount -o remount,size=128M /dev/shm &> /dev/null
  echo -n performance
| sudo tee /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor &> /dev/null
  if ip addr | grep wlan &> /dev/null
    echo -n "1-1.1:1.0" | sudo tee /sys/bus/usb/drivers/smsc95xx/unbind &> /dev/null
  jackd -P84 -p128 -t2000 -d alsa -dhw:UA25 -p512 -n2 -r44100 -s -P -Xseq
&> /dev/null &

This is the first section of the script. An if clause that checks if JACK is already running and if that’s not the case the system gets set up for low latency use, a simple check is done if there is an active WiFi adapter and if so the ethernet interface is disabled and then on the last line JACK is invoked. Notice the ALSA name used, hw:UA25, this could be different on your RPi, you can check with aplay -l.

jack_wait -w &> /dev/null

jack_wait is a simple app that does nothing else but checking if JACK is active, the -w option means to wait for JACK to become active.

if ! pidof linuxsampler &> /dev/null
  linuxsampler --instruments-db-location $HOME/LinuxSampler/instruments.db
&> /dev/null &
  sleep 5
netcat -q 3 localhost 8888
< $HOME/LinuxSampler/SalamanderGrandPianoV3.lscp &> /dev/null &

This stanza checks if LinuxSampler is running, if not LinuxSampler is started and 5 seconds later the config file is pushed to the LinuxSampler backend with the help of netcat.

while [ "$STATUS" != "100" ]
  STATUS=$(echo "GET CHANNEL INFO 0" | netcat -q 3 localhost 8888
| grep INSTRUMENT_STATUS | cut -d " " -f 2 | tr -d 'rn')

A simple while loop that checks the load status of LinuxSampler. When the load status has reached 100% the script will move on.

jack_connect LinuxSampler:0 system:playback_1 &> /dev/null
jack_connect LinuxSampler:1 system:playback_2 &> /dev/null
#jack_connect alsa_pcm:MPK-mini/midi_capture_1 LinuxSampler:midi_in_0 &> /dev/null
jack_connect alsa_pcm:USB-Keystation-61es/midi_capture_1 LinuxSampler:midi_in_0
&> /dev/null

This part sets up the necessary JACK connections. The portnames of the MIDI devices can be different on your system, you can look them up with jack_lsp which will list all available JACK ports.

jack_midiseq Sequencer 176400 0 69 20000 22050 57 20000 44100 64 20000 66150 67 20000 &
sleep 4
jack_connect Sequencer:out LinuxSampler:midi_in_0
sleep 3.5
jack_disconnect Sequencer:out LinuxSampler:midi_in_0
killall jack_midiseq

This is the notification part of the script that will play four notes. It’s based on jack_midiseq, another JACK example tool that does nothing more but looping a sequence of notes. It’s an undocumented utility so I’ll explain how it is invoked:


<command> <JACK port name> <loop length> <start value> <MIDI note value> <length value>

jack_midiseq Sequencer 176400 0 69 20000 22050 57 20000 44100 64 20000 66150 67 20000

JACK port name: Sequencer
Loop length: 4 seconds at 44.1 KHz (176400/44100)
Start value of first note: 0
MIDI note value of first note: 69 (A4)
Length value: 20000 samples, so that's almost half a second
Start value of second note: 22050 (so half a second after the first note)
MIDI note value of second note: 57 (A3)
Length value: 20000 samples
Start value of third note: 44100 (so a second after the first note)
MIDI note value of second note: 64 (E4)
Length value: 20000 samples
Start value of third note: 66150 (so one second and a half after the first note)
MIDI note value of second note: 67 (G4)
Length value: 20000 samples

Now the script is finished, the last line calls exit with a status value of 0 which means the script was run successfully.

exit 0

After making the script executable with chmod +x ~/bin/piano and running it you can start playing piano with your Raspberry Pi! Again, bear in mind that the RPi is not made for this specific purpose so it could happen that audio starts to stutter every now and then, especially when you play busy parts or play more than 4 notes at once.

Using a Raspberry Pi as a piano: quick demo

Using a Raspberry Pi as a piano

First Dutch Raspberry Jam

The first Dutch Raspberry Jam will take place on Thursday September 26 at the Ordina HQ in Nieuwegein. I’ve offered to do a presentation about doing real-time audio with the Raspberry Pi which has been accepted. Internet visibility of this event is minimal at the moment though, let’s hope it caches on.

So expect a presentation/demo about using your Raspberry Pi as a sequencer, synthesizer, sampler or virtual guitar amp. I will show how to configure, tweak and tune your RPi for real-time, low-latency audio and what the possibilities of such a set-up are. I’ll probably do a live demo too of some tracks generated by one or more RPi’s

Ordina Raspberry Jam

Raspberry Pi Playlist @ AutoStatic’s YouTube channel

First Dutch Raspberry Jam

More ARM goodies II

Received the BeagleBone Black (BBB) and the MK808 with a RK3066 SoC. My first impressions are really positive. Especially the BBB is quite an awesome device that I’m probably going to use a lot in favor of the Raspberry Pi. At first glance I had something like, the BBB blows the RPi away, but as soon as I started looking for documentation on how to put Debian on it for instance it became clear that the RPi is still the device to beat. The RPi community is huge, documentation for it is well laid out and working with the RPi is just so easy. The BBB on the other hand lacks a vivid community, is $10 more expensive and a lot more difficult to work with. Take the Debian install for example, seems quite some work to get that going.

The MK808 is surely an improvement over the UG80X I already own. It comes with a HDMI port instead of a HDMI plug, has an extra USB OTG port, a heatsink, hardware serial console access, a reset button and a power indicator LED. The pre-installed Android version looks better too. I flashed my RT kernel recovery image on it, inserted the Micro SD from my UG80X and it booted without any issues. So I’m going to pursue my goal to get a real-time, low-latency environment running on a RK3066 based device on the MK808 and find another purpose for the UG80X.

Edit: Getting Debian to work on the BBB is actually quite easy:
Next time I’ll promise to make better use of my Google skills.

More ARM goodies II