passthrough is intended as a simple solution for routing midi between external devices connected to norns. it may be considered midi thru for norns, defined at a script level, with a few extra functionalities added.
with passthrough, norns can be used as a midi routing hub. the internal nomenclature of the library defines two midi ports as either device or interface.
a device is conventionally dedicated to controlling, for example, a midi keyboard, sending note or control change data. an interface, often a device that generates sound, receives this incoming data and does something with it such as play incoming notes.
it is possible to send midi clock messages to the device from the interface. one peculiar feature of passthrough, that extends a typical midi thru functionality is that incoming notes from the device can be quantized to a scale if desired.
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send notes through norns from a usb midi controller to a midi-compatible synthesizer.
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scale quantization of incoming midi note data from controllers
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by leveraging callbacks at a script level, incoming midi events can be shared between norns engines/parameters and external hardware
norns + midi compatible hardware.
if your hardware does not offer midi via usb, an interface such as an iConnectivity mio helps to connect with 5-pin midi ports.
passthrough is intended to be easy to get up and running, and can be installed and used in two ways - standalone or embedded.
installing standalone has the advantage of being possible to use passthrough with various scripts, whereas embedded places it within a single script, making that script more portable for sharing.
the installation has been successful if passthrough appears in the script's params menu.
as a standalone script and library, it is available to download from maiden's project manager or by running the following command in maiden's repl:
;install https://github.com/nattog/passthrough
passthrough can be used with the example scripts or by attaching it to external scripts, by adding the following code at the head of the script file:
if util.file_exists(_path.code.."passthrough") then
local passthru = include 'passthrough/lib/passthrough'
passthru.init()
end
passthrough can be added to a specific script by copying this file https://github.com/nattog/passthrough/blob/main/lib/passthrough.lua to the lib directory of a script. If lib does not exist, it will need to be created. the final path should look like [script_name]/lib/passthrough.lua.
then add the following code to the main script file:
local passthru = include ("lib/passthrough")
passthru.init()
passthrough needs a small amount of plumbing to ensure that midi is routed to the correct destination.
ensure first that you have your midi hardware connected to norns. navigate to the passthrough section in the params menu and select your device and interface.
next, ensure that the device channel and interface channel options are correctly set. by default, these do not change the midi channel used so if your device is sending data on midi channel 1, the interface will receive data on channel 1.
at this point, the core functionality is setup for midi data being passed from device to interface.
cc msg direction toggles between unidirectional and bidirectional. unidirectional is device to interface, whereas bidirectional allows the interface to send control change to the device.
clock device allows the device to follow the clock events of the interface, which is useful if the device has an arpeggiator or sequencer functionality.
quantize toggles note quantization. this allows note data to be restricted to scales. root and scale control the transposition and scale type respectively.
scripts can listen for midi events handled in passthrough and define their callbacks. The following example updates a script's freq and amp parameters based on midi device events
-- Midi event, fires when Midi data receieved
function midi_device_event(data)
local msg = midi.to_msg(data)
if msg.type == "note_on" then
hz = music_util.note_num_to_freq(msg.note)
params:set("freq", hz)
params:set("amp", (msg.vel / 127) * 100)
end
end
passthru.user_device_event = midi_device_event
raise any issues experienced with passthrough either in the thread on lines or by logging a new issue on the github repo.
interested in adding a new feature or making changes? any pr is always welcome.