variax

Command line control for Line 6 James Tyler Variax (JTV) guitars through the Line 6 Variax USB Interface: select models, set volume, tone and any tuning, switch on a 12-string sound, and watch what the guitar's knobs send.

It also works as a MIDI bridge. Together with the Variax USB Interface, variax midi lets any MIDI device or app (a guitar effects processor, a MIDI foot controller, MainStage or a DAW) change the guitar's model and tuning, for example on every patch change. Until now that needed a Line 6 Helix, POD HD or another device with a VDI jack; now a Mac running variax and the USB interface the guitar came with are enough. See Control from MainStage, a DAW or a MIDI controller.

Line 6 has retired the Variax line, including the USB interface and its software. This is an unofficial community project to keep these guitars useful. It is not affiliated with or endorsed by Line 6 or Yamaha.

Requirements

• macOS. Windows and Linux are not supported yet; see Contributing.
• Python 3.11 or newer.
• A Line 6 Variax USB Interface, connected to the guitar's VDI jack.
• The guitar switched on: with the USB interface the guitar runs on its battery, and only switches on with a 1/4" cable plugged into its output jack.
• No other program using the interface: close Line 6 Central and Workbench HD.

Tested on a JTV-59. Other JTV models and the Variax Standard use the same interface and probably work; the model names in the output come from the JTV-59/69 Pilot's Guide.

Install

pip install variax

or with uv or pipx: uv tool install variax, pipx install variax.

From a clone of this repository, install it as a command that runs the code in the clone, so your changes take effect straight away:

uv tool install --editable .

Usage

variax send -n 'lester 5'                   # select a model: bank + pickup position (1 = bridge, 5 = neck)
variax send -n 'Rbilly 3'                   # names are case-insensitive, hyphens optional
variax send -p 18                           # or by program number (0-59 knob positions, 60-104 factory models)
variax send -n 'factory spank 5'            # the factory version of a model
variax send -p 18 --volume 100 --tone 64    # volume and tone, 0-127
variax send -n 'lester 5' --tuning dadgad   # a tuning by name; without --keep, the tuning knob
                                            # must be on MODEL
variax send --tuning dadgad --keep          # works with the tuning knob anywhere and stays through
                                            # model changes until you turn the knob; whole semitones
variax send -s 'E B E G# B E'               # any tuning, low E first, as notes...
variax send -s '-1 -1 -1 -1 -1 -1'          # ...or semitones from standard (fractions allowed)
variax send --tuning none                   # no pitch shift: strings sound as physically tuned
variax send --twelve-string on              # 12-string sound; "off" to stop
variax send --modeling off                  # the magnetic pickups; "on" to switch modeling back on
variax send -n 'semi 1' --dry-run           # show the MIDI messages without sending them

Tunings and the tuning knob. Without --keep, a tuning becomes the current model's own tuning: the guitar only plays it with the tuning knob on MODEL, and a model change resets it. With --keep, the tuning plays with the knob in any position and stays through model changes, until you turn the knob; it only takes whole semitones.

On/off options take on/off, yes/no or true/false. --modelling works too.

send always sends in the same order (modeling, model, volume, tone, tuning, 12-string), so tone and tuning follow the model change in one command. They have to: a model change reloads the stored model, with its own tone and tuning (only a --keep tuning stays). Nothing is ever saved to the guitar, so your presets stay untouched.

--strings takes six notes or numbers, low E string first, separated by spaces or commas: 'D A D G A D', 'Eb Ab Db Gb Bb Eb' (or ♭/♯), '-2 0 0 0 -2 -2', or a mix. A note means the nearest pitch to the standard string, at most a tritone up or down, so B on the low string is a baritone B; add the octave for anything further, e.g. 'E1 A1 D2 G2 B2 E3' for an octave down (standard is E2 A2 D3 G3 B3 E4).

--tuning knows the factory tunings of all JTV models by name:

Name	Tuning, low to high string	Also recognized
standard	E A D G B E
drop d	D A D G B E
half down	Eb Ab Db Gb Bb Eb	1/2 down
drop Db	Db Ab Db Gb Bb Eb
one down	D G C F A D	1 down
dadgad	D A D G A D
open d	D A D F# A D
blues	D G D G B D	blues g
reso	G B D G B D	reso g
open a	E A C# E A E
baritone	B E A D F# B
drop c	C G C F A D
m3 down	Db Gb B E Ab Db	minor 3rd down, minor third down, min3 down
drop b	B Gb B E Ab Db
M3 down	C F Bb Eb G C	major 3rd down, major third down, maj3 down
drop Bb	Bb F Bb Eb G C

Case, spaces and hyphens don't matter (Drop-D, dropd), except that m3 (minor third) and M3 (major third) are told apart by the case of the m. Other names are looked up among the tunings stored on your guitar's tuning knob, so your own custom tunings work by name too.

Other commands:

variax monitor     # print what the guitar sends as you turn its knobs; run
                   # 'variax tunings --save' first to see tuning knob names
variax tunings     # the tunings on the tuning knob, and the current model's tuning
variax tunings --save   # also save the knob's tunings to tunings.json
variax midi        # a virtual MIDI port for MainStage and other apps (see below)
variax models      # list all program numbers and model names
variax dump        # the current model's settings, including its tuning and 12-string state
variax read 0x41C 6   # read words of the current model (for exploring; see docs/PROTOCOL.md)
variax --help      # all commands; variax send --help for all send options

variax tunings --save writes the tunings stored on the guitar's knob to tunings.json in the current directory, with the names and strings as the guitar reports them (which may differ from the factory tunings). variax monitor and variax midi use this file, when it is in the current directory, for the tuning knob's names and tunings; without it, monitor shows the knob's positions as numbers.

The file looks like this:

{
  "tunings": [
    {"name": "STANDARD", "strings": "E A D G B E"},
    {"name": "DROP D", "strings": "D A D G B E"}
  ]
}

Control from MainStage, a DAW or a MIDI controller

variax midi creates a virtual MIDI port called Variax that other apps can send to, and translates what they send into changes on the guitar. The guitar's own knob changes come back out of the same port. It runs until you press Ctrl-C.

Your settings file

The bridge reads its settings from variax.toml and your tuning knob's tunings from tunings.json, both in the directory you start it from. To set up your own:

1. Make a folder for your setup and go there:

   mkdir -p ~/variax && cd ~/variax
   

2. Create variax.toml, with every setting, its default and what it does:

   variax midi --write-config
   

3. Edit variax.toml to suit your setup. Every setting is optional: you can delete the ones you don't change. The bridge checks the file when it starts and names any mistake.

4. Save your guitar's tuning knob tunings to tunings.json (guitar connected and switched on):

   variax tunings --save
   

5. Start the bridge from that folder:

   cd ~/variax && variax midi
   

Without a variax.toml the bridge uses the defaults, and without a tunings.json it reads the knob's tunings from the guitar when it starts. To browse all settings without installing anything, see src/variax/default.toml, the file --write-config writes.

Sending to the bridge

In MainStage (or any app), choose Variax as a MIDI output and have your patches send these on channel 1 (the defaults; all of it can be changed in variax.toml):

Send	Does
Program Change 0–104	selects that model (as variax models lists them)
CC 7 / CC 79	volume / tone, 0–127
CC 84	tuning: 0 = none, 1–11 = the tuning knob's tunings, 12+ = your own [tunings]
CC 85	12-string: 0–63 off, 64–127 on
CC 86	modeling: 0–63 off (the magnetic pickups), 64–127 on
CC 20–25	each string's tuning, low E first: 64 = standard, 52–76 = −12 to +12 semitones
CC 26–31	each string's fine tuning in cents, low E first: 64 = 0
Line 6 SysEx	passed to the guitar unchanged (other SysEx, such as the probes Logic Pro sends to every new port, is ignored)

Volume, tone and tuning use the same CC numbers the guitar uses to report its own knobs, so a MainStage control on CC 7 both sets the guitar's volume and follows its volume knob. MIDI monitors show CC 84 as "Portamento Control", its name in the MIDI standard; the guitar simply uses that number for its tuning knob. If an instrument receives this port and reacts to it, set another tuning number in variax.toml.

With program_change = "patches" in variax.toml, a Program Change applies a whole [patch.N] instead: model, volume, tone, tuning, 12-string and modeling in one go, for controllers that can only send one Program Change per patch. variax.toml documents every setting, including patches.

Tunings work as with variax send: by default (tuning_method = "model") the tuning knob has to be on MODEL; with tuning_method = "keep" it works with the knob anywhere, in whole semitones. The bridge sends up to about 25 tuning changes per second; when an app sends faster, it skips to the newest value.

How it works

The Variax USB Interface doesn't show up as a MIDI device: it uses its own USB protocol, so variax talks to it directly with libusb. Underneath, it carries plain MIDI messages plus Line 6 SysEx. The protocol notes, with every message and how it was found, are in docs/PROTOCOL.md.

Contributing

Help with Windows and Linux support is very welcome, as are reports from other Variax models. What is known so far:

• Linux: the kernel's own Line 6 driver (snd-usb-variax) claims the interface, so variax would have to detach it, and users need a udev rule for access without root.
• Windows: libusb needs the WinUSB driver on the interface (e.g. installed with Zadig), which replaces Line 6's driver while it is installed.

The tests run without a guitar:

uv sync
uv run pytest

Credits

Reverse engineered by Peter Hulst, by monitoring the guitar and capturing the USB traffic of Line 6 Workbench HD. With thanks to:

• Joe Bear, for the tuning SysEx behind --keep, and the authors of the community "Variax MIDI reference" spreadsheet, for the magnetic/modeling switch and the factory program numbers.
• Markus Grabner and the Linux kernel Line 6 driver (sound/usb/line6/variax.c, and the older staging driver), for the handshake and the model data requests.
• The VGuitar Forums and Line 6 Community discussions of the Variax and its VDI interface.

License

MIT. Line 6, Variax, James Tyler and the guitar names used for the models are trademarks of their respective owners.