ZDoom

After looking at this again, it appeared that [b]CheckNumForName()[/b] cannot be used with long filenames.
In this case, only the first 8 characters of the filename do matter for file lookup.

So, either short names, which would be [b]This_is_[/b] in the given sample, or full names, i.e. with paths and extensions, must be used for music aliases.
Inconsistent alias resolution is fixed in [url=https://github.com/coelckers/gzdoom/commit/cad14d1c935f3a869ecccedf67de32702820743f]cad14d1[/url].

$musicalias D_RUNNIN music/This_is_a_hoedown_song_that_I_like_very_much.mid

There is a discrepancy between [url=https://github.com/coelckers/gzdoom/blob/f398819ce38c49b8781f70fa335fa9adff580862/src/sound/s_advsound.cpp#L1199]SNDINFO parsing[/url] and [url=https://github.com/coelckers/gzdoom/blob/f398819ce38c49b8781f70fa335fa9adff580862/src/sound/s_music.cpp#L464]alias resolving[/url]. Notice [b]CheckNumForName()[/b] vs. [b]CheckNumForFullName()[/b] calls in these code snippets.
Usage of the first function will make the sample work as expected. The second function will require not only an extension added to a file name, but a full path.[code]$musicalias D_RUNNIN music/This_is_a_hoedown_song_that_I_like_very_much.mid[/code]

I tried the following:

$musicalias D_RUNNIN This_is_a_hoedown_song_that_I_like_very_much.mid
$musicalias D_RUNNIN "This_is_a_hoedown_song_that_I_like_very_much.mid"
$musicalias D_RUNNIN music/This_is_a_hoedown_song_that_I_like_very_much.mid
$musicalias D_RUNNIN "music/This_is_a_hoedown_song_that_I_like_very_much.mid"

None of the above did what was required, but there was a difference between them and the example. In the example, the music for MAP01 didn't work at all and the title music just kept playing after map01 had started. With the above, the original D_RUNNIN played during map01.

Doing so in the example file does not seem to change anything.

For long file names you have to include the extension.

http://edthebat.com/doom/musicaliastest.pk3

In the attached example, D_RUNNIN is meant to be replaced with another file. But its name is longer than 8 characters, so the music does not play.
There is a commented line to perform the same action with a different (identical) music file, but since its name is under the 8 character limit, it works correctly when uncommented.