Show HN: Perfect Bluetooth MIDI for Windows
Hi HN, I'm Erwin. I built a small free open-source utility that bridges Bluetooth LE MIDI keyboards into the new Windows MIDI Services stack so any DAW or Web MIDI app can use them as if they were wired.
I bought a Roland FP-90X piano partly because it had Bluetooth MIDI. On my Windows 11 PC, pairing succeeded, but my DAW couldn't see the keyboard, and notes I sent from the PC never made the piano sing. After a regrettable number of evenings, I'd separated this into three independent bugs stacked on top of each other.
The first one is the famous one: Windows only natively exposes BLE-MIDI through the WinRT API, which almost no DAW polls. So even when pairing succeeds, MIDI apps still don't see the device. The usual workaround is MIDIberry + loopMIDI, but I couldn't get that combination to work reliably in my case, and I wanted a single-app solution. The new Windows MIDI Services stack ships with a feature called loopback endpoints: anything written to one comes out the other, and any winmm/WinRT/WMS app sees them as normal MIDI ports. So the app does WinRT BLE-MIDI in, WMS loopback out. That solved direction one, piano to PC.
Direction two, PC to piano, still didn't work. NoteOn writes were getting ATT-acked, but the piano stayed silent. I tried both write modes (some BLE-MIDI firmware silently drops one or the other), poked the proprietary ISSC characteristic. Every variant ATT-acked, every variant produced silence. So the bytes were reaching the piano. Something above the GATT layer was discarding them.
After ruling out pairing, encryption, write-mode, and proprietary characteristics, the only obvious lever left was the MIDI channel itself. The FP-90X has a panel setting called Transmit Channel, default 1. Yet it turns out the FP-90X actually receives on channel 4 (and it can't be changed). Notes I sent on channel 1 were being GATT-acked and silently dropped at the synth engine because they weren't on the channel the engine was listening to. Zero feedback at any layer. The fix had to live up at the application layer, so I added a Detect button that plays N test notes ascending on each channel from 1 to 16: you count the notes you actually hear, and that number is the receive channel. Saved per BLE MAC, about 75 seconds, done forever per piano.
Tech stack: .NET 10, Avalonia for the UI (the BLE/MIDI side is Windows-only but the UI layer is portable), Microsoft.Windows.Devices.Midi2 packages for WMS, Windows.Devices.Midi (WinRT) directly for BLE rather than relying on Korg's older WinMM driver. MIT, single self-contained ~21 MB exe, no installer, no telemetry, no account.
I built it for myself and use it with my FP-90X to play through a few apps and Web MIDI sites. Pete from the Microsoft Windows MIDI Services team commented positively on the BLE integration when I shared it on r/synthesizers (https://www.reddit.com/r/synthesizers/comments/1szvuiq/comme...).
Site (with screenshots): https://mayerwin.github.io/Perfect-Bluetooth-MIDI-For-Window...
Source: https://github.com/mayerwin/Perfect-Bluetooth-MIDI-For-Windo...
Long-form technical writeup with the full debugging story: https://dev.to/mayerwin/why-your-bluetooth-midi-keyboard-sil...
Personally tested with my FP-90X only. The BLE side is generic, so other keyboards (WIDI Master, CME, Yamaha MD-BT01, Korg microKey Air, ROLI Seaboard, etc.) should work, but I haven't confirmed individually. Device test reports, issues, and PRs very welcome.
For what it is worth, Microsoft is in the process of rolling out Windows Midi Services for Windows 11.
https://microsoft.github.io/MIDI/
A few more years and we might be able to approach Atari ST levels of MIDI performance…
Never gonna happen. The architecture of modern hardware and operating systems won't allow for that kind of low latency and jitter.
Specifically for Windows, the Intel 2001 Guidelines and Microsoft WHQL (Windows Hardware Quality Labs) which prohibit the use of MPU401-style interfaces, as well as direct driver access to either the serial or parallel ports.
Doing Direct-To-Bus MIDI handling can't be replicated in modern architecture like the ST was configured.
That said, given the popularity in analog semi-modulars to be used as DAW outboard with MIDI over USB implementations that add latency and jitter, is it even a consideration for most users?
Ableton and other performance oriented DAWs automatically compensate for MIDI and audio latency caused by plugins and devices; in Ableton's case it will delay the audio by the overall system latency, and/or bypasses plugin delay compensation only for armed/monitored tracks, making them more responsive.
The real answer to the question is, as always, to use hardware sequencers and control voltage triggered off your master clock or DAW. SQ-64 is as rock solid as an Atari ST for CV work, although the 64ppqn limit doesn't match the Atari ST' 384pqqn capabilities. That said, standard MIDI Beat Clock is much lower at 24 PPQN. If you want to go all Autechre/Aphex Twin there's plenty of ways to skin that cat.
If you care about timing over Midi, use MTC not Midi Clock. Because receivers have to derive clock frequency by counting pulses, Midi clock is inherently unstable.
Midi Time Code is SMPTE.
Fun, I do the opposite, explicitly use Midi Clock so everything is purposefully a tiny bit out of sync, seems to sound better to me, "Midi clock is inherently unstable" is the feature I like :)
There are technologies like MTS (MIDI timestamping), where you basically send timestamped data early to the interface so that it can then play them out exactly (or more exactly) at the right time. This was initially made by MOTU but I think the implementation in Core MIDI is based on it.
Emagic and Steinberg also implementation of this (AMT in case of Emagic, LTB for Steinberg IIRC.
This only really works with recorded data of course. It's also very old already (like 25 years old), I'm not sure how well it is still supported in current DAWs.
With these technologies, timing should be as good or better as on an Atari.
Why on earth is the "Windows MIDI Services is Here" thing a slider/carousel with one element in it? Why are the buttons completely misplaced with no margin between them? Has a human seen and tried this before they just deployed everything and went live?
Because slopsoft.
Valid questions even if all of them are rhetorical.
Most choices are not between bread and cake.
Most choices are between bread and nothing.
Good engineering is the art of good enough.
Outrage is hardly warranted.
> Good engineering is the art of good enough.
Sure, agree. When will this website reach the state of "good enough"?
> Outrage is hardly warranted.
Agreed, but I also don't see any outrage in any of the comments for this submission, what outrage are you talking about?
It's good enough if it conveys the information to its intended audience.
If the comment isn't outrage, it's even less warranted.
Why so mean? You can look at all of the commits and see that the same dev who has been writing these drivers and apps pretty much single handedly has been making commits on the site for the past few years. https://github.com/microsoft/MIDI/commits/main/docs
You can even PR fixes if you want to show off your web dev skills.
+1 to this. Psychlist1972 / Pete is good people.
Pete is one of those rare Microsoft developers who is actively interacting with customers publicly. He's active on the Gearspace forums where musicians hang out, helping people with their Windows issues relating to operating system level audio issues. Here's his Gearspace thread announcing the new Windows 11 MIDI drivers:
https://gearspace.com/board/new-product-alert-2-older-thread...
I wish there were more people like Pete working at Microsoft. He's someone who is genuinely trying to improve the OS and make it a great experience for users.
EDIT: Re-read the original post and I see Pete even checked this project out and commented on Reddit. Sorry I missed that the first time.
Multi-client support? I must be dreaming!
Wow very cool project! I will test it out later today - i have always been using cabled connection for my midi keyboard
> Windows only natively exposes BLE-MIDI through the WinRT API, which almost no DAW polls.
I haven’t used Windows for ages. Does this mean that almost every Windows user with any Bluetooth MIDI keyboard is unable to use it out of the box with their DAW without installing additional third-party software?
Does it apply even to latest version of the very widely used DAWs like Ableton, Pro Tools, FL Studio, Reason, and Reaper?
If you use a Mac, you'd be amazed at how many things can't be done on Windows without 3rd-party software.
Do you know how to spot a Windows user ? They print-and-scan to merge their PDFs.
This is a weird comment because I feel the same about getting macOS to a useable place.
I probably have 5 or 6 things installed on my Mac like Scroll Reverse and Rectangle, just trying to beat the window manager into something that resembles useable.
Actually I thought the same for macOS for certain things, like window management was way better on Windows than on macOS (snapping etc.) Luckily after years macOS finally has something decent to organize windows. I know that there were 3rd party apps like rectangles but something simple like organizing windows missing from a desktop OS always felt weird.
That is a nice function of Preview indeed.
On the other hand, at least since a couple of releases, I have lots of troubles with the highlight annotation in Preview, especially in PDFs with tables. So much so that I have to resort to 3rd party software for that (PDF Expert in my case).
But yeah, PDF support is basically native in macOS since Mac OS X.
That wouldn't surprise me.
Surprisingly Windows audio stack is a mess. I have a mini keyboard with Bluetooth and it was an adventure to get it working in Windows. In Linux it was pretty much plug and play.
Low latency audio drviers are also messy in Windows when not using an audio interface with well written ASIO drivers. Pipewire in Linux is much easier to configure. Looks like MacOS also does not have this driver problem.
It is surprising. Because most audio plugins and DAWs support only Windows and MacOS.
If you are using Windows professionally for audio, you will be using ASIO. So in practice, this is not really a problem. Especially considering that ASIO drivers often even perform a bit better than their CoreAudio counterparts and don't have hidden doublebuffering.
macOS also seemed or seems to have quite a few problems with DriverKit USB drivers for large channel count interfaces.
Wow. That looks really painful. I have multiple pianos, always used cable because I wanted it to work without problems in Linux and Mac. Also I can't stand delays.
I have created 20 utils or so with the help of Claude, in order to practice multiple things like reading sheet music, or rhythms, or different scales. I never expected it to be that useful as my new Yamaha was bought before Claude existed, and having a cable that just works is so great.
I have spent way less effort doing all my utils than this man into just connecting its machine.
Before using it with Claude I used them a lot with Synthesia and GarageBand, but with Claude is like having a personal trainer.
This is really interesting. Windows device handling can be tricky sometimes, especially when things work at one layer but fail silently at another. The channel detection approach is clever.
Did you try https://github.com/celtera/libremidi ? It should poll BLE devices
All of my synths are hooked up via USB or Focusrite interface (wired MIDI) because that makes sense for my setup, but this could be cool for more portable setups. The big question is what does your average latency look like?
I've been looking at building a "Linux MIDI gadget" to send signals from my Casio DG20 to my PC over BLE -- this is just what i need for the PC end
Tried with the Yamaha Seqtrak on Windows 10, didn't work.
Impressive work! Alas I don’t use windows but if I did I would certainly check this out.