After seeing this tweet from the creator of Orca I was curious to try it myself.
Here are the steps I needed to make it work on Ubuntu 18.04.
I'm new to most of this, so please correct me if I understood anything wrong.
First you will need a software synthesizer. I chose TiMidity++. To install it on Ubuntu I mainly followed the steps from this guide, which I reproduce here:
If you don't have the universe repository activated yet run:
sudo add-apt-repository universe
Install TiMidity++ and the freepats samples:
sudo apt-get install timidity freepats
You might need to activate the following kernel modules:
sudo modprobe snd-seq-device
sudo modprobe snd-seq-midi
sudo modprobe snd-seq-oss
sudo modprobe snd-seq-midi-event
sudo modprobe snd-seq
If you don't have node installed yet, install it with:
sudo apt-get install nodejs
The steps to install Orca are taken from the README of the project:
git clone https://github.com/hundredrabbits/Orca.git
cd Orca/desktop/
npm install
Open a terminal were you run the command
timidity -iA
and keep that terminal open!
This gives me the following output:
Requested buffer size 32768, fragment size 8192
ALSA pcm 'default' set buffer size 32768, period size 8192 bytes
TiMidity starting in ALSA server mode
Opening sequencer port: 130:0 130:1 130:2 130:3
Requested buffer size 32768, fragment size 8192
ALSA pcm 'default' set buffer size 32768, period size 8192 bytes
You see, that the program opens some ports. In the next step will choose one of those to have Orca send its MIDI output to.
Open another terminal where you run Orca in by navigation to the desktop
subdirectory of your Orca folder and type
npm start
Next we need to choose our MIDI devices as described in the FAQ's of project by pressing
ctrl+. in Orca to open a browser console (you might need to choose the correct console tab at the top).
Type terminal.io.listMidiDevices() in the console to obtain an output similar to (expand the output in your console if needed):
terminal.io.listMidiDevices()
(5) [MIDIOutput, MIDIOutput, MIDIOutput, MIDIOutput, MIDIOutput]
0: MIDIOutput {connection: "closed", id: "6FF5590044F4859ED50C5167BCFE9700A1798E39AA55A628E86D39011FAECD5D", manufacturer: "", name: "Midi Through Port-0", state: "connected", …}
1: MIDIOutput {connection: "closed", id: "574FB441DEDADDE2DB06598767A3088744994E3AEA26BA638F8C51D004D8D333", manufacturer: "", name: "TiMidity port 0", state: "connected", …}
2: MIDIOutput {connection: "closed", id: "8C1A6E287845194CE38B5B5181F731AE63D54D00681076DF9905B3658DF86248", manufacturer: "", name: "TiMidity port 1", state: "connected", …}
3: MIDIOutput {connection: "closed", id: "A32276E0B2B7CB991939F210D7542BA7A43CE9E97E78C9F5B8D85BA2AC033C5F", manufacturer: "", name: "TiMidity port 2", state: "connected", …}
4: MIDIOutput {connection: "closed", id: "CBE9CBC37EE04BD5C4039207BE53A9C0E36ED85542FEF3FCF6AF4D0901370F08", manufacturer: "", name: "TiMidity port 3", state: "connected", …}
length: 5
__proto__: Array(0)
So we see that the TiMidity++ ports are devices 1 to 4.
Now set the MIDI Device e.g. to the first of those by typing terminal.io.setMidiDevice(1) in the console.
This should come with a confirmation similar to:
/home/bernd/projects/Orca/desktop/sources/scripts/io.js:62 Set device to #1 — TiMidity port 0
Now close the web console window.
Hit ctrl+o in Orca to get a dialog for opening a .orca file.
There is the example directory in your Orca folder.
Choose the midi.orca file in that directory and you should here a single note playing in a loop!