When working on the BulkyMIDI-32, a piece of hardware running the MT32-PI software, I mostly ended up using standard 5-pin MIDI-cables for most of it. Except in some cases there simply isn't room to do so, or I wanted to use a piece of equipment that had a 3.5mm TRS jack on it instead - commonly referred to as TRS MIDI.

As for TRS MIDI - there are two types - type A and type B. Both of them are associated with premium brands and charge a premium price for a cable that we ordinary people see as a cable that looks exactly like a stereo audio jack on one end, and a 5-pin MIDI plug on the other. At one point I assume one expensive brand looked at the other, then swapped the available two wires around to ensure that people bought their cables in the ensuing confusion.

As for getting such a cable, I had problems getting one. In part because sites like AliExpress sells cheap ones listed as a MIDI TRS-cables, then sends you something that has a whole other wiring than either standard - my only guess are that these were for use with older tape decks that also used 5-pin DIN-connectors. The other was that I couldn't find an expensive one from a company that would actually ship one to me without charging more than an arm and a leg.

So I took took what I had - plenty of 5-pin MIDI cables and 3.5mm stereo audio cables, then put together this adapter to plug in between. It has a set of jumpers, move them around to select if the thing on the end expects type A or type B wiring. Probably shouldn't use it for anything professional, but I'm not a professional - for me, it is good enough.