MIDI over TRS
MIDI through an ordinary 3.5 mm jack instead of the five-pin DIN — sensible for small gear, and for a decade without an agreed wiring.
The 1983 DIN socket is taller than many modern synths are thick. During the 2010s manufacturers started shipping a breakout cable and fitting a minijack instead. The signal is unchanged, a current loop at 31.25 kbit/s, but it only needs three of the DIN's five pins, and those fit on tip, ring and sleeve. The trouble was that nobody had agreed which went where.
Korg put the current source on the ring and the receiving side on the tip. Arturia and Novation did the opposite. The result was two incompatible schemes in the same connector, and a cable that looks right and does nothing. The MIDI Association standardised Type A, Korg's layout, in 2018. Type B lives on in shipped hardware, and the little adapter box with an A/B switch has become a product category of its own.