This wasn't an issue in the past when keyboard manufacturing companies put a 5 Din MIDI connector on keyboards, but nowadays all you have is a USB B (USB to HOST).

How do you connect two keyboards that only have a USB to HOST for MIDI?

Essayist and simplest way is to use a computer or tablet as the bridge so that you have full control of what goes where. (Note not all Midi USB keyboards are supported by tablets)

Bill

Thank you abacus, I already knew that, but I'm looking for something that doesn't involve tablets or computers.

In that case you need to purchase a USB MIDI Host Box, such as the Kenton USB Midi Host or Disaster Area MIDI Host, and also have look on Google.

If you are into it, there is also a DIY version here but you would be better off using a computer or Tablet.

Bill

I'm a big fan of the CME products, for wireless AND wired MIDI. Give their H4 interface a look. USB-C, USB-A, 5-pin MIDI & wireless MIDI (WIDI) with an optional internally mounted accessory board.

Very affordable, very reliable.