A free browser based MIDI drum sequencer / recorder

Resources:

Shared kits
Shared songs/demos
Upload a kit
Upload a song/demo

Londonsen Moore Roland round robin kits. Rename them from .zip to .rar before you unpack.

NEW: BOFF round robin maker - v 1.6.1 updated!. Round robin samples sound great. This is an attempt at turning a single hit into a more interesting rotating set. It's fairly straight forward. Load a sample then hit generate. Start a preview pattern playing and change parameters <> regenerate. I particularly like cranking up the tails, pitch and volume bars. When your test pattern sounds good, export the samples in a zip ready to load into your boff lane.

Are you a real MIDI nerd if you haven't tried to build a MIDI sequencer?

What is Box Of Frogs - Free

BOFF is my second attempt to do something interesting with web midi. My first was a sysex patch librarian for the PWM Mantis synthesiser.

Essentially BOFF is a realtime* 7 track recordable MIDI drum sequencer. It isn't realtime in so far as it has a buffer scheduling 100ms into the future. But it is realtime in so far as you program it, then record a midi file of yourself playing it.

Some features:

• Selectable MIDI output device.
• Set up your 7 midi drum lane/instruments in the drum map. They can have a name, midi note, default velocity and accented velocity. The free version is locked to MIDI ch10.
• BOFF generates 8 random patterns and you can play pattern 1 by pressing space.
• a,s,d,f,g,h,j,k switch patterns in place/live
• You can mute / solo any combos as you play. Check out the help file for more keys.
• As you are jamming you can randomise the whole pattern, or individual instruments.
• If you don't like what you did, press backspace to undo.
• There's a toolbox with some editing functions. E.g
  • Add a velocity groove to all instrument lanes, or individual lanes.
  • Add some triplets.
  • Experiment with different shorter pattern lengths.
  • Turn on pattern resync to pull you back to the 1 every 4,8, or 16 beats.
• Don't forget to save your set of patterns.
• Now the cool bit. It has a built in recorder to capture a full jam.
• Once you have captured a performance it will let you listen back and export a MIDI file for your DAW.
• It captures tempo changes if you want to drop some in.

If you encounter a bug or have suggestions for improvements, I'd be delighted to hear from you.

Demo: https://youtu.be/pExvKblUg00?si=MyHIVH8PgeuWPnqR. (same as embedded above).

2.2 new features demo: https://youtu.be/HFhCyNvvxxs.

download here: box-of-frogs-free-2-2.html

Requirements

• Modern Chromium-based browser recommended (Chrome, Edge, Brave etc.).
• Works entirely offline after download.
• No installation required.
• It has been tested in Edge on Win11
• I wouldn't leave it playing while you change tabs. Most browsers put the tab to sleep and it gets a bit stuck,

If you like this...

I've already made Box Of Frogs PLUS

Some hilights:

• More lanes. 10 lanes on any channel with optional unique MIDI out device per lane
• Adjustable midi latency compensation per lane
• A lane can be a drum or a pitched synth or a midi CC
• Transpose pitched lanes by MIDI in
• An arp
• A velocity or CC value lfo per lane
• Quantised patch changes with per lane patch pre delay
• Madder than this Box Of Frogs!
• More

Get in touch for more info here.

NEW: 05/07/2026 - BOFF 1.5b has an audio engine for playback and export!

Originally conceived as a browser based midi performance tool. Now non hardware users can get in on the fun. Because AI said why not? done.

• Instead of using MIDI hardware, tick use internal sampler.
• You can drag up to 32 samples onto each drum lane. Using a folder if your browser/os support it. Edge on win11 does. Chrome on my chromebook doesn't. I can still hilight all the samples and drop them at the same time.
• You can load and save sample kits.
• By default they play in round robin.
• There is a manual mode where round robin is turned off. Instead you can address any of the 32 samples in the pattern to do stuff like pitched sequences.
• You can tell a lane to choke another lane. Good for closed on open hihats.
• Or assign to a choke group and all lanes in the group choke each other. Good for effects and performance.
• Once you have captured a performance, you can export to WAV.
• This lets you bounce down many lanes to one, to continue playing over the top.
• Talking of bouncing, I added a toolbox feature "Loop every X bars". This lets you play back a captured bounce of any size whilst jamming within your 16 step pattern.
• If you get a good synth line going, you can lock the lane and it will persist across pattern changes.
• You can render each lane to it's own WAV file. It respects all chokes. So even though you are only rendering out the open hi hat, it is still choked by the closed, albeit silently.
• You can save the entire state to one file. This lets a friend open and play it with no dependencies, or just lets you get back to exactly where you left off.

NEW: 06/07/2026 - BOFF 1.6b - Changes to what is stored in local storage and when.

It makes working with the mapper more predictable.

NEW: 12/07/2026 - BOFF 1.8 - Fix plus an extention to loop every X behaviour

Loop every X didn't respsect the start cell and always looped on step 1. That's fixed but it has evolved in this release. It's now called Repeat every X, and the main change is you can choose a step number to get polyrhythms going. I've put an example state file in my pcloud folder with a couple of patterns at the beginning that use it. You still use it to playback bounced renders if you want. In which case apply it to the 1, and choose not to choke. So your render keeps it's tail as it loops. The other choke settings are choke normal drum hits but not repeated hits. So essentially the repeated hits can be played polyphonically over themselves. Or choke everything. For when you are using it for strange drum hits that should work with the normal drum hits.

NEW: 18/07/2026 - BOFF 2.2 - Madder by far

There's too much to list for now. Basically it works how i wanted now and i've included nearly everything i could think of. I'm going to try and switch to youtube shortly and show the new stuff.