Euphonium does not have native sound/playback
S5 - Suggestion
Users have raised this numerous times in the forums. Reasons given are similar to https://musescore.org/en/node/203491, "None of these a part of GM, so would need some specilized and additional soundfont."
As of MuseScore 3.6.2, euphonium uses the tuba sound, which causes its own issue, documented at #324917: Euphonium uses tuba sound by default, no playback above C5.
Even if there is not an easy fix available, at least possible workaround or links to external soundfonts can be collated here.
For a link to an external soundfont (Euphonium Hedsound sf2) see:
Thank you. Using this or the euphonium sound from Symphonic Sounds (https://musescore.org/en/comment/1097492#comment-1097492) would be workarounds as well, albeit dependent on 3rd party soundfonts. There seems to be an option/initiative to extend the tuba sound range upwards as per #324917: Euphonium uses tuba sound by default, no playback above C5 to give a built-in workaround for euphonium playback.
Thanks for pointing me here, @Jojo-Schmitz.
Please note that you made this a dual-topic-issue now: I specifically requested Muse Sounds for Euphonium, wheras this was all about Sound Fonts., according to the forum discussions.
Deliverying Muse Sounds doesn't solve this one (only https://musescore.org/en/comment/1157305#comment-1157305), delivering Sound Fonts doesn't solve https://musescore.org/en/comment/1157305#comment-1157305.
... or rename this one to "add both SF and Muse Sounds for Euphonium". But that's quite some work to do in one ticket.
I would keep separate tickets for SF and Muse Sounds.
I don't think it'd happen to the standard soundfont.
In reply to I don't think it'd happen to… by Jojo-Schmitz
That's a fair assumption. And probably the best solution.
Now with MS4 out, can I still choose another sound font? Does the workaround still apply?
Suggestion, as it isn't a bug