Marc Nostromo

A view askew on music technology

August 14, 2014
by nostromo
0 comments

Re-tuned

I’ve noticed my nostromotron was slightly off due to rounding error in the code. I’ve also taken the opportunity to check the analog oscillator scaling over the note range. The end result sounds way less toyish and it feels smoother now.

You can grab the last version of the code over at github.

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May 29, 2014
by nostromo
0 comments

MFB-522 Sample pack

I had Ian’s MFB-522 for an afternoon. It’s a fantastic little drum machine so I decide to make a sample pack with it. It won’t replace the fun to tweak the real thing but might come handy.

Download here: MFB-522

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May 25, 2014
by nostromo
10 Comments

Using ODroid U3 and arch-linux for Audio applications

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The ODroid U3 surely rocks the house. With 3 usb port it can fit any combination of external control you would like [Launchpad, nanoKontrol, Audio out, ...] , a processing power that blows the Rpi to dust,  it shines it the best standalone cpu platform I’ve come across so far.

Installation-wise, I installed arch-linux and compiled my synthesis framework in about 3h without a glitch (except for the built-in audio not being recognised by ALSA), and it auto-boot to any app in about 13 seconds.

I enjoy now close to unlimited number of Braider voices while the Rpi puked on three.

So, no matter whether you want to write synthesis software or use any of the Linux classics like pd, super collider, etc.. I’d hugely recommend it.

 

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January 13, 2014
by nostromo
0 comments

Telsonic Segment Jam

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Now that I’ve tamed the feedback part on TelsonicSegment, it’s a lot easier to explore its sound space without getting [too] all over the place. Here’s a quick jam done this morning using a simple setup with my RaspPie running Telsonic Segment fed through a DOD 250 clone into a cheap Behringer mixer clone.

Loads of flavors !

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January 6, 2014
by nostromo
1 Comment

Installing ArchLinux on Raspberry Pi for headless audio

Since I’m re-doing a fresh install of a SD card on my Raspberry Pi, I thought I’d document the process as I go, in case it is useful for other people (or for my future reference in the most likely case we’re I’ll screw my current SD). I”ve chosen to use ArchLinux over Raspbian because it boots faster and has a smaller footprint. Since I’m mainly interested in using the Raspberry pi headless – without any screen or keyboard attached – it makes sense to have a reduced system to start with. On my current SD, it takes about 10 seconds to boot into the app of my choice, that’s way better than bringing any of my computer back from sleep and firing the equivalent app.

Important note 1: As always, this is heavily time dependent and I can’t guarantee the exactness of this post at any other future dates.

Important note 2: When you changes files on the Rpi and need to reboot, don’t plug the power out. You have a lot of chances files where not committed to the SD yet and all your edits will be lost

1 – Build a SD card

The steps are explained over here, in the installation tab. It’s the pretty standard “download the image and do a SD card dump” procedure. Under linux, use dd. With Windows, you will need Win32DiskImager. Once the image is done, remove it from you computer, stick it into the Rpi’s SD slot and boot it up. The image is setup to use DHCP, so if you you can simply power the Rpi connected to an ethernet cable and – provided you can find its ip –  you can directly ssh to it. Otherwise, you will need to connect it to a screen and keyboard and login that way. The default username/password of the image is ‘root’ / ‘root’. The default hostname is ‘alarmpi’.

2 – Setup the package manager

Since you will need to install some additional libraries / packages, it’s a good idea to setup archlinux’s package manager, cutely named ‘pacman’. You can find information about the process over here (look for update system). You can update the system too if you want, nothing wrong with getting the latest while we’re setting up.
The steps I’ve followed are:

  1. Create a pacman key:

    # pacman-key –init

  2. Update the system (this will take a while):

    # pacman -Syu

  3. Reboot

    # reboot –reboot

3 – Adding packages

Now you need to find and install packages that are missing. You can look for packages through keywords using

# pacman -Ss keyword

And install them using

# pacman -S keyword

In my case I ended needing was sdl, alsa and jack:

# pacman -S sdl
# pacman -S alsa-utils
# pacman -S jack

4 – Testing usb midi/audio

In theory, you don’t really need to execute this step (since everything should work smoothly) but I always like to double check things:

Connect a USB audio device then type

# aplay -l

You should see an entry both for the internal audio device (bcm2835) and USB audio.

card 0: ALSA [bcm2835 ALSA], device 0: bcm2835 ALSA [bcm2835 ALSA]
Subdevices: 8/8
Subdevice #0: subdevice #0
Subdevice #1: subdevice #1
Subdevice #2: subdevice #2
Subdevice #3: subdevice #3
Subdevice #4: subdevice #4
Subdevice #5: subdevice #5
Subdevice #6: subdevice #6
Subdevice #7: subdevice #7
card 2: Device [USB PnP Sound Device], device 0: USB Audio [USB Audio]
Subdevices: 1/1
Subdevice #0: subdevice #0

Then plug in a MIDI device and see if alsa recognises it:

#  aconnect -o

client 14: ‘Midi Through’ [type=kernel]
0 ‘Midi Through Port-0′
client 20: ‘Launchpad’ [type=kernel]
0 ‘Launchpad MIDI 1′

5 – Removing the default pi audio output

Since the built-in audio out of the raspberry pi is only good for deaf people, it makes sense to remove it. Raspbian has a sysem that makes any usb audio the default one but arch linux doesn’t. Since we want it to work with anything we would plug into it, we’ll just get rid of the bcm2835 so it doesn’t get in our way. To do so, edit the file /etc/modules-load.d/raspberrypi.conf and remove / comment the bcm2835 related modules (bcm2708-rng, snd-bcm2835)

6 – Autobooting

If we want to use our raspberry pi as a headless sound device, it’d be nice to get it to start some programs automatically at boot time. So far, the easiest way I’ve found is to use crontab.

Crontab has a special syntax that allow some command to be executed at boot time. So we’ll create a shell script in our root folder and get cron to execute it everytime we restart the Rpi. If we want to change the start sequence later, we simply need to update the shell script.

Start by editing root’s crontab:

# crontab -e

And add the following line:

@reboot /root/autostart.sh > /root/autostart.log 2>&1

which tells to execute a shell script – autostart.sh – located in the root home and to log all output from it into autostart.log

Now go in the root folder (cd /root) and create autostart.sh containing, for example, the following:

echo “hello world”
exit 0

Make sure the autostart.sh is executable by

# chmod a+x autostart.sh

And reboot the rpi:

# reboot –reboot

When you reconnect to the Rpi, the root folder should now have a file autostart.log containing

hello world

Bingo ! Now we can start any favorite program to start at boot time !

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October 18, 2013
by nostromo
13 Comments

Casio LaunchPie

Lately I’ve been interested in combining a standalone synth running on the Raspberry Pi with a Launchapad setup in ‘grid scale’ mode – like push does – to have a small standalone synth I could quickly power to practice scales or play along tracks without the need of a dedicated computer setup.

Here’s a first step showing the Rpi booting and activating the launchpad. It doesn’t sound great right now but is a good enough proof of concept to pursue the effort.