JS-80

Play two flexible, polyphonic, 80's style synthesizers and a sequencer with a MIDI keyboard and your computer keyboard, all in a single browser window. (Or produce distorted, disconnected clicks and noises if your device doesn't have enough CPU capacity for this app. If this happens, try reloading the page and select lower poliphony for the synth modules.)

Connect your MIDI keyboard, then hit the button below:

QWERTY module poliphony:

MIDI module poliphony:

Known problems and quirks

Realtime audio manipulation may require a lot of CPU resources, so it's recommended to close other browser tabs and CPU-intensive programs. Also, this may drain your battery, so it's recommended to connect the charger.
Unfortunately, the wave folder and the distortion effects have aliasing issues in some configurations, and reducing these seems to require trade offs that introduce more problems elsewhere.
As of 2022 June, in order to use a MIDI keyboard as an input device in Firefox, you have to:
- set dom.webmidi.enabled to true in the about:config settings (and make sure that midi.testing is false),
- and if this is the first time you want to use your MIDI keyboard with this app, then install this site permission addon.
As of 2022 June, MIDI keyboards don't work at all in Chromium on Ubuntu, due to a bug in its snap packaging.
It is possible to put together a patch which causes digital distortion in the sound or no sound at all. If you experience similar sound issues, try to adjust the settings of your patch.

Tips and tricks

Keyboard shortcuts are shown on the screen between brackets: for example, pressing 1 selects the first bank of the Sequencer, and pressing A will play the note A on the virtual keyboard. (Pressing the shift key gives the note a little extra velocity.)
The keyboard shortcut labels correspond to the standard US QWERTY keyboard layout, but it's the physical location of the keys that matters, not the label on the computer keys. For example, if you use a QWERTZ keyboard layout, then you have to press the key which has the label Y near the left shift key in order to play the lowest C note of the on-screen virtual piano keyboard.
MIDI controllers like the pitch wheel or the modulation wheel usually go from 0% to 100%, but you can make them, for example, go from 20% to 70% using one of the Macros at the bottom of the screen. For example, assign Flex 1 to a synthesizer parameter, then assign the modulation wheel (modulation (CC 1)) to the input (IN) of the first Macro, then set its MIN and MAX value to 20% and 70% respectively.
All changes to the Sequencer (including turning it off or switching to a different bank) take effect only after the current set of beats has finished playing to the end, so you don't have to be very precise with your timing. The only exceptions are the tempo, arpeggio, gap, and detune parameters which take effect immediately, allowing for example gradual, continuous tempo changes while playing.
If you set the Target parameter of the Virtual keyboard to Sequencer root note then you can change the modality of the scale while it's playing. Example:
- Configure the following Scale notes: C, D, E, F, G, A, B. (Make the unneeded ones empty.)
- Set the BPM to 30.
- Configure the first beat to play 1, 3, and 5.
- Configure the second beat to play 2, 5, and 7.
- Hit the space key, so the Sequencer starts repeating a C-major chord, followed by a G-major (2nd inversion).
- Press A, so in the next iteration and onwards, the Sequencer will play A-minor and E-minor (2nd inversion).
- Press Z again to go back to C-major and G-major (2nd inversion).
Note that when the Virtual keyboard is set to drive the Sequencer like this, then pressing the keys won't make any sound on its own.
By default, the MIDI module has 8 notes polyphony and the QWERTY module has 6. The Sequencer reserves up to 5 notes from the module to which it is assigned, reducing the polyphonic notes of the module that can be played manually while the Sequencer is turned on.