Handel is a small procedural programming language for writting songs in browser.

The Handel Interpreter interprets Handel programs and plays compositions in browser, thanks to Tone.js.

Try the Handel Web Editor here: Handel Web Editor

Check out the Handel Github repo: Handel on Github

Join the Handel forum to ask questions and showcase compositions. Also check out the Contributing guidelines.

soli deo gloria


Add the below to your html document:

<script src="https://unpkg.com/handel-pl"></script>

You're all set!


Install Handel with the following:

npm i handel-pl

And import Handel with the following:

import * as Handel from 'handel-pl';


Example Handel Snippet

    chunk example 
        play E3, C3, G3 for 2b
    run example with sound piano, loop for 5 

See the Examples folder here for example Handel programs and inspiration.

Example Using Handel In Browser

function clicked(){
            chunk example using somePlayable 
                play somePlayable 
                rest for 1b
            save myPlayable = Eb3 for 1b
            run example using myPlayable with sound piano, loop for 5 
document.addEventListener("click", clicked);

Note that you pass the Handel code into the RunHandel function Handel.RunHandel(someHandelCode).

To compile to midi, pass a config object to the RunHandel function with outputMidi set to true.

const config = {outputMidi: true};
Handel.RunHandel(`start play E4 for 1b finish`, config);

Additionally, you can use the StopHandel function to stop a running Handel program. Handel.StopHandel()

Getting started

Handel programs are contained within the start and finish keywords. Below is a complete Handel program:

    play E4 for 1b

The program above only plays 1 note. But it's a start!

Let's play something

You can be play notes and chords using the play command. Below is an example program that plays a note, then a chord:

    play C#3 for 1b
    play E3, G3, A4 for 1b

Note the syntax above. A play command begins with the play keyword, then a note or chord (a list of notes separated by commas) follows.

Lastly play commands need a duration. The play commands above end with 'for 1b'. This states how long the particular note or notelist (chord) should be held.

Phew! We're getting somewhere.

Let's rest

Similar to the play command, a rest can played using the rest command. Below is an example program that rests for 1 beat then plays a note for 2 beats.

    rest for 1b
    play G5 for 2b

But are there Variables?

tl;dr Here is some example usage of variables in Handel

save myplayable = E4, F4, G3 for 3b
save myduration = for 1b

play myplayable
rest myduration

You can declare Variables in Handel. Variables store two builtin types in Handel: Playables and Durations.

We've already seen Playables above. Playables are a note or notelist (chord) followed by a duration. Here are some example playables.

Bb3 for 1b
D#6, E#6, G3 for 1b

no promises that the above chord sounds pleasing to the ear :p

Durations are the keyword for followed by a beat.

A beat is any whole number followed by the letter 'b'

All together, here some example durations:

for 1b
for 2b
for 16b
for 32b

Finally variables!

To store a playable or a duration use the save keyword, followed by a variable name, an equal sign and a playable or a duration.

Variable name must contain only lowercase letters, and no numbers. Variable names must also not be any of the reserved keywords in Handel. (See the Reserved Keywords section below).

Below is an example program using variables.

    save myplayablenote = E2 for 2b
    save myrest = for 2b

    play myplayablenote
    rest myrest
    play myplayablenote
    rest myrest

OK! So far so good!

Blocks loops

Handel (v0.2.0 and greater) supports block loops. Block loops begin with the block keyword and end with the endblock keyword and the amount of times a block should loop (a loop customization).

Here is an example of a block loop in Handel.

    play C3, E3, G3 for 1b 
    play D3, F3, A3 for 1b 
endblock loop for 10

Procedures (I thought this was a procedural programming language?)

Procedures in Handel are called chunks. You can conceptualize a chunk as a song track. When ran, chunks play at the same time as other run chunks and the global track. Chunks must begin with the chunk keyword and end with the endchunk keyword.

Below is an example program with a kick drum and a piano, playing together.

    chunk backbeat using myplayable
        play myplayable 

    chunk mykeys 
        play E3, G3, A3 for 1b
        play G3, A2, C3 for 1b
        play F3, A3, C3 for 1b
        play D3, F2, A3 for 1b

    run mykeys with sound piano, loop for 2

    save myplayable = A1 for 1b

    run backbeat using myplayable with sound kick, loop for 8

Both the 'backbeat' chunk and the 'mykeys' chunk above play together (not one after the other). This behavior allows multitrack songs to be created with Handel.

More on procedures (chunks) and their syntax

Procedure declaration (creating chunks)

As noted above you can create chunks with the chunk keyword. The name of the chunk (the chunk name) follows the keyword.

This chunk name must be all lowercase letters, no numbers and cannot be one of Handel's reserved keywords. (See the Reserved Keywords section below).

After the chunk name, you can optionally add parameters. A list of comma separated parameters can follow the using keyword.

Together you get the following: chunk somechunkname using someparam, anotherparam

After the optional parameter list, you can add a body to the chunk. This is a function body (what you would like to happen when the chunk is ran).

Lastly the chunk must be ended with the endchunk keyword.

Running Procedures

You can run a chunk using the run keyword.

To run a chunk use the run command followed by the name of the chunk.

If the chunk has parameters, a you must use a matching number of comma separated arguments.

Here is an example running two chunks. One chunk requires arguments the other does not.

    chunk noargs
        play C3 for 1b

    chunk withtwoargs using argone, argtwo
        play argone
        play argtwo

    run noargs
    save somevar = Cb4 for 1b
    run withtwoargs using E3 for 1b,  somevar

Note that saved variables, playables, or durations, can be used as arguments when running a chunk.

OK! Now to configuring a run of a chunk.

Configuring a run of a chunk

You can configure a run of chunk by adding the with keyword and a comma separated list of customizations to the end of a run command.

There are three main customizations: bpm, sound, and loop.

You can use bpm keyword to set the bpm of a run of a chunk.

For example bpm 120

You can use the sound keyword to set the instrument of a run of a chunk.

For example sound piano

The current available sounds to choose from are: piano, synth, casio, kick, snare, hihat

You can use the loop keyword to set the amount of times the run of a chunk shoud loop for.

For example loop for 10

All together you can configure a run of a chunk as follows:

    chunk withargs using somechord 
        play somechord 

    run withargs using E3, G3, F3 for 1b with bpm 100, loop for 8, sound piano 

Above we've got a chord, played with a piano, looping 8 times, with a bpm of 100!

Custom Instruments

Handel (v0.4.0 and up) allows custom instruments to be loaded into Handel Programs. Instruments can be created and added to a run of a Handel program as follows.

let myinst = Handel.MakeInstrument({
    A1: 'https://tonejs.github.io/audio/casio/A1.mp3', 
    A2: 'https://tonejs.github.io/audio/casio/A2.mp3'
let config = {}
config.instruments = {funkyinst: myinst} 
        load funkyinst as funky 
        chunk example 
            play E4 for 4b
        run example with sound funky
`, config)

The MakeInstrument function wraps Tone.js's sampler constructor. It takes a urls object as its argument. This urls object, maps note names matched to their location (locally or not). One or more mappings can be used.

After making an instrument above, we add it to our config object and run the Handel program with that config.

Within the Handel program we load the instrument as follows: load configInstrumentName as nameOfInstrumentWithinHandel

Note: this feature makes your Handel program less portable but gives you the freedom of using arbitrary instruments in your Handel program.


Note: A musical note. 7 octaves are available.


Notelist: A list of notes. Together this list of notes forms a chord. (6 notes maximum).

C2, E2, G2
C4, Eb4, G#3

Beat: A number of beats. A whole number followed by the character 'b'.


Duration: An expression that represents the amount of beats to play or hold for.

for 1b
for 2b

Playable: A note or a notelist, followed by a duration.

C1, F1, E1, D1, for 1b
D1 for 2b

play: A command to play a note or notelist for a given duration. Play commands can also take a loop customization.

play C1, F1, E1, D1, for 1b
play D1 for 2b loop for 5

rest: A command to rest for a given duration.

rest for 1b
rest for 2b

save: A command to save a variable (see above section on variables for more details). Only playabes and durations can be saved in variables.

save myplayable = e2 for 1b
save myduration = for 1b

load: A command to load custom instruments into Handel (see above section on custom instruments for more details).

load someinst as instname

block: Used to declare a loop. (see above section on block loops for more details)

    play Gb3 for 2b
    rest for 2b
endblock loop for 10

chunk: used to declare a procedure. (see above section on procedures for more details)

chunk mybassline
    play G1 for 2b

using: Used to prepend a list of paramaters for a chunk.

chunk mypiano using nicechord
    play nicechord 

run: Used to run a chunk. (see above section on running procedures for more details).

run mypiano using E2, C#2 for 1b

with: Used to customize a given run of a chunk. (see section on procedures above for more details)

run mybassline with bpm 115

bpm beats per minute (bpms are best synced with values under 1000).
loop: amount of times to loop.
sound: instrument to use.
volume: percentage volume of a chunk (0 - 100).
pan: amount to pan the sound of a chunk (0 - 100). Note: 0 = hard-left, 50 = center, 100 = hard-right.
reverb: reverberation duration in miliseconds (>= 1).

run mybassline with bpm 90, loop for 2, sound kick, volume 50, pan 70, reverb 10000

Sounds: possible sounds that can be used to customize a run of a chunk. (piano, synth, casio, kick, snare, hihat)


Reserved Keywords


























All note names are reserved keywords, ex. C4, Bb1. For this reason use only lowercase letters with no numbers in variable names.