Show HN: I built a WebMIDI sequencer to control my hardware synths

#1

Post by simplychris » Thu, Dec 11, 2025, 5:27 PM UTC

Hey HN,

I’m an ex-Google engineer trying to get back into music production.

I needed a way to sequence my hardware synths using AI contexts without constantly switching windows, so I built this.

It runs entirely in the browser using WebMIDI. No login required. It connects to your local MIDI devices (if you're on Chrome/Edge) and lets you generate patterns.

Tech stack: [React / WebMIDI API / etc].

Link: www.simplychris.ai/droplets

Code is a bit messy, but it works. Feedback welcome.

Show HN: I built a WebMIDI sequencer to control my hardware synths
simplychris.ai

Re: Show HN: I built a WebMIDI sequencer to control my hardware synths

#2

Post by vermon » Wed, Dec 17, 2025, 8:20 AM UTC

Vibe coded? Asking because it looks very similar to my vibe coded webmidi project which is a beatmatching practice for DJ’s :) https://beat.maido.io/

Re: Show HN: I built a WebMIDI sequencer to control my hardware synths

#3

Post by rcarmo » Wed, Dec 17, 2025, 8:45 AM UTC

This is pretty cool in concept. Need to go and get stuff to plug into my laptop to test :)

Re: Show HN: I built a WebMIDI sequencer to control my hardware synths

#4

Post by thenthenthen » Wed, Dec 17, 2025, 9:16 AM UTC

rcarmo wrote: post #3

This is pretty cool in concept. Need to go and get stuff to plug into my laptop to test :)

Does webmidi works over usb-otg? Then maybe it could run from a phone or tablet!

Re: Show HN: I built a WebMIDI sequencer to control my hardware synths

#5

Post by piltdownman » Wed, Dec 17, 2025, 10:15 AM UTC

thenthenthen wrote: post #4

rcarmo wrote: post #3

This is pretty cool in concept. Need to go and get stuff to plug into my laptop to test :)

Does webmidi works over usb-otg? Then maybe it could run from a phone or tablet!

Yeah you can connect via USB MIDI using an OTG adapter by enabling "USB MIDI Peripheral mode" in Developer Options. There's plenty of videos on how to set it up from the Android MIDI Arranger App community - just N.B. you may need a powered USB hub depending on your use-case.

Re: Show HN: I built a WebMIDI sequencer to control my hardware synths

#6

Post by gbraad » Wed, Dec 17, 2025, 10:15 AM UTC

I wrote mine also, integrating an Akai Fire, at https://music.gbraad.nl/meister as part of a tool to do live performances. This controls some of my remix tools, mixxx and vj tools too.

Edit: my usecase is more integrating different tools and devices, Bitwig, Electribe, mixxx, my mod/protracker remix tool, etc. I guess your usecase is more to generate music, less my thing, but possible. I just have a particular sequencer/tracker use. Generation happens in bitwig

Re: Show HN: I built a WebMIDI sequencer to control my hardware synths

#7

Post by gbraad » Wed, Dec 17, 2025, 10:18 AM UTC

thenthenthen wrote: post #4

rcarmo wrote: post #3

This is pretty cool in concept. Need to go and get stuff to plug into my laptop to test :)

Does webmidi works over usb-otg? Then maybe it could run from a phone or tablet!

I use my tools from a linux machine (reliable) and Android (OK). I got a h4midi wc to improve the setup. Webmidi and JS is not idealz as wakelock is needed and javascript is actually slow.

Re: Show HN: I built a WebMIDI sequencer to control my hardware synths

#8

Post by Aldipower » Wed, Dec 17, 2025, 11:15 AM UTC

This does not solve the underlying problem at all, which makes today's MIDI, coming from a normal computer, almost unusable for serious sequencing. This is timing and jitter issues! So, may I asked, what is the actual use-case for this sequencer? I would like to see/hear some music you made with it. Or is this just for the sake of using AI?

Re: Show HN: I built a WebMIDI sequencer to control my hardware synths

#9

Post by Libidinalecon » Wed, Dec 17, 2025, 12:20 PM UTC

Aldipower wrote: post #8

This does not solve the underlying problem at all, which makes today's MIDI, coming from a normal computer, almost unusable for serious sequencing. This is timing and jitter issues! So, may I asked, what is the actual use-case for this sequencer? I would like to see/hear some music you made with it. Or is this just for the sake of using AI?

If you have hardware synths you are going to have a decent midi and audio interface that this is not a problem. It wasn't even a problem 25 years ago. There is no reason for consumer grade audio to be able to do this because most people will never use it.

Re: Show HN: I built a WebMIDI sequencer to control my hardware synths

#10

Post by Aldipower » Wed, Dec 17, 2025, 12:45 PM UTC

Libidinalecon wrote: post #9

Aldipower wrote: post #8

This does not solve the underlying problem at all, which makes today's MIDI, coming from a normal computer, almost unusable for serious sequencing. This is timing and jitter issues! So, may I asked, what is the actual use-case for this sequencer? I would like to see/hear some music you made with it. Or is this just for the sake of using AI?

If you have hardware synths you are going to have a decent midi and audio interface that this is not a problem. It wasn't even a problem 25 years ago. There is no reason for consumer grade audio to be able to do this because most people will never use it.

I have maybe 20 hardware synths and I do a lot of sequencing. And yes it wasn't a problem 25 years ago, that is exactly why I still use an Atari STe! :-) But today it is a problem. It is just not possible to do complex and tight sequencing today with a normal Win, Mac or Linux computer. Even with my RME PCIe card. Your argument, "it wasn't a problem decades ago, so it cannot today either" is simply not correct.