Well, sometimes sound cards have large current sink ability on TXD line, but I would not count on it. It depends on sound card (era, make, model) and where the signal is coming from anyway. Sometimes it may come directly from a weak LSI chip. So if you know your sound card, go ahead, it should not break anything.

However, if you put some buffering there, it will always work with all sound cards and protect it by blowing your buffer first in case of ESD or something (although the next device should have a optocoupler so they are galvanically isolated so this should not happen).

With a buffer, you can also use spare gates to drive multiple outputs or activity LEDs.

Speaking of MIDI ports, does any one have a schematic for an Voyetra V22 Dual Port ISA 8bit midi card?

This was discussed when I created a small Gameport->MIDI project that would allow MIDI and the gameport to be used at the same time. Still haven't gotten around to building it, mostly because of me being cheap and having a hard time finding a good place to get it done. See it here:
Small warm up project - Gameport/MIDI box

thanks for the info!
I'll go the 74LS00 way , alexanrs's way is very nice too but it would look ugly without a pcb 😉