Hamby wrote on 2023-11-18, 19:22:

I have a MIDI keyboard with usb-b connection, and no midi connection. […]
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I have a MIDI keyboard with usb-b connection, and no midi connection.

I would like to use it with my vintage computers, such as my 486 running DOS, or my Amiga or Mac SE/30, but they obviously lack USB.
But there are midi adapters for all of them (like the game/midi port on the 486's sound card, to which I've attached a midi adapter).

Is there any (fairly simple) way to connect the USB-B of the keyboard to the MIDI-IN of my midi adapter?
I'd like to use the keyboard for input, and my MT-32 for output.

Something like this should do it :

# for USB 1.1 MIDI devices :
https://www.amazon.com/CAMOLA-MIDI-Host-Inter … r/dp/B08MZY59B7

# for USB 2.0 "high speed" MIDI devices ( seems backward compatible with USB 1.1 MIDI devices) :
https://www.amazon.com/CAMOLA-Speed-Converter … 1/dp/B09S5YC2Z9

Just an example, not an recommendation or endorsement .

EDIT : If you just want to use the keyboard as controller, see also this https://www.serdashop.com/USBMIDIHost

darry wrote on 2023-11-18, 19:52:

EDIT : If you just want to use the keyboard as controller, see also this https://www.serdashop.com/USBMIDIHost

I think that's exactly what OP needs... but that price is rather excessive. You can see from the screenshots that it's only a PIC MCU that sells for less than $10, so you could save quite a bit by making your own from practically any MCU with a programmable USB Host port.

jmarsh wrote on 2023-11-18, 20:42:

you could save quite a bit by making your own

If you already have the skills, tooling, time, consumables, and reasonable availability of parts.

Another option is to use an intermediate Windows or Linux computeras a makeshift MIDI bridge using Virtual MIDI cable or Jackd .