Note: Browser data storage only exsists within your web browser's cache data, and is only available on this device. Clearing your browser's data (cookies/cache) could also remove songs saved here. Save to a local file or cloud storage for long term storage.
This will generate an array suitable for including in you own web apps making use of JSME: The JavaScript Music Engine.
Basic Usage: Click cells to select. Use the Note Builder bar to create notes.
The HUB button allows you to store and export your songs, as well as load from some preset songs. The PLAYER button controls playback, and also is where the tempo/BMP is configured.
The Ins/Del buttons insert a row above the current selected row, or delete the current selected row. The +CH adds a channel to the end, the -CH deletes the current selected channel.
Shift-Click allows selecting multiple cells. 📄 will copy those cells to the clipboard. 📋 will paste those selected cells at the current selected location. ❌ will clear the cells.
The second row has the Note Builder buttons (all Note Builder functions can be performed from the keyboard shortcuts). C-B select the note, #/b for sharp and flat, and - for no accent. OCT sets the octave, 4 being middle octave. The Sustain checkbox switches from using a note selection, or selecting how many 1/8th notes a note should be played for. VOL is the note's volume relative to the master volume. SET sets the current note. and SET+ sets the current note, and advances the cursor when the currently selected note would stop playing. You will see a blue bar appear to the right when using any note longer than a 1/8th note. This bar shows how many 1/8th note steps the note will play for.
For specifics on JSME and how to use it in your own programs, go to https://www.stellimare.com/JSME-JavaScript-Music-Engine/. The rest of this information relates specifically to the JSME Composer tool.
This tool is a work in progress.
JSME is a pure JavaScript based player. It needs no external audio files, only an array with playback instructions. It makes use of modern browsers sound context to synthesize notes which is very similar to early computers "chip tune" playback systems. The file format is detailed in the "LLM Prompt Helper," which you can copy-paste into a LLM and see if it'll generate some sensible music for you. You can, of course, use the editor to manually compose your own music (which I recommend if you have an music skill of your own).
This tool allows you to save files to your browser, or to a file that you can share. It also has import/export function were you can import or export a raw JS array to edit or copy into your own JavaScript web app making use of JSME. Browser storage should only be used for temporary backups. You may find backups of your songs temporally stored there.
Remember: The user must interact with the web page before audio can be played. Clicking a "start" button is perfect.
LLM's like Google Gemini, are able to generate music data for playback using this system. The prompt below will provide instructions for the LLMs to follow. Your success will vary (all the example music here was generated with Google Gemini prompts).
Act as a composer for JSME: JavaScript Music Engine and generate a song as a raw JavaScript array. Your output must only contain the raw array with no comments nor markdown prose, and no empty strings. Each array index represents a 1/8th note tick. You must use sparse arrays with consecutive commas to represent empty space or rests. The first element of the array contains metadata, only the "emd-metadata" and tempo tags are required, the rest are optional. The format of the metadata is '[ ""emd-metadata" , ["TAG","Value"],["TAG","Value"],...]'. The following array elements are the channel lists. They take the form of '[ [<instruments data>], [<note>,<note>,...]]'. The notes take the form of <duration><name><octave><volume>. The duration takes two forms, one is the note form where 1 (or none) ,2,4,8,16 are for a whole, 1/2, 1/4, 1/8. and 1/16th note duration (if it is a whole note the 1 can, and should, be omitted, also note the scale is 1/8th, so a 1/16th note would only play for half of a tick, with a forced 1/16th pause); the other is S+n, where where 'n' is the number of 1/8th note steps to play. Next is the note name:C,D,E,F,G,A,B (this is the only required note, do not use '-' for a pause, simply add empty cells for the consecutive 1/8th note pauses). Next is the optional accent, # for sharp and b for flat. Next is the octave with 4 being the middle octave (4 is optional, it is only required for those not in the 4th octave). Next is the volume when the note is to play at a lower volume than 100% of the master volume. This is a single digit fractional number, so ".5" is 50% volume and ".9" is 90%, and nothing is 100%, and .95 isn't allowed because it's two digits. The instrument data is an array that contains information about the waveform to use and takes the form of [ramp,filter,resonance,waveform]. Never use "-" for the note name or "." alone without a number as neither will play. Example (there is no limit on the number of channels, but keeping it under 8 is easier to manage):
[ ["emd-metadata", [ ["tempo", "120"], ["title", "Crossed Buns"], ["author", "JSME"], ["notes"," optional long-form comments and notes"]] ], [ [1.0, 1100, 1, "sawtooth"], [ "4B.8",, "4A.8",, "2G.9",,,, "4B.8",, "4A.8",, "2G.9",,,, "16G.7", "16G.7", "16G.7", "16G.7", "16A.7", "16A.7", "16A.7", "16A.7", "4B.8",, "4A.8",, "2G.9" ] ], [ [1.0, 150, 0, "sine"], [ "S+4G2.6",,,, "S+4G2.6",,,, "S+4G2.6",,,, "S+4G2.6",,,, "S+4G2.6",,,, "S+4D2.6",,,, "S+4G2.6",,,, "S+4G2.6" ] ] ]
Instruments presets:
Last Updated: January 28, 2026
Your privacy is important to us. This policy explains what information our server collects and how it is handled. Because this is a client-side application, most of your data stays exactly where it belongs: on your own device.
Like most website operators, our server automatically collects standard "log data" that web browsers and servers typically make available. This includes:
This information is used solely for technical maintenance, security monitoring, and understanding general traffic patterns. We do not sell, rent, or share this information with any third parties.
Our application integrates with Google services for advertising and cloud storage (Google Drive). Please note:
Server logs are periodically deleted and are not used to track individual users across the web. The logs are only intended to determine website usage, trends, and abuse. They are not used to identify specific users, nor are our logs shared with any third party (unless an abuse issue has been identified, then the attaking IP address(es) will be reported so ISPs can take the appropriate actions).
We may update this policy from time to time to correct errors or omissions, but the intent of the privacy policy will remain with regard to JSME Composer.
Feel free to drop a tip below. Thanks!