Create a blank new playlist and drag all your target files from Explorer into foobar2000, and have a look at how they group.
If they don't group as you expect, then you select all in the Playlist (CTRL+A) and go into Properties (ALT+ENTER)
and see if some Tag name which should be common to all files is maybe not.
The Album tag should be common to all, and so should the Album Artist tag.
The Artist tag should be unique for each track. It is also known as the 'Track Artist' tag if 'Album Artist' tag has a value (i.e., is not blank ).
If you want each unique artist name to appear with the track title then you need to include the %track artist% variable in your
formatting for the Track Title column of your Playlist Viewer; maybe something like: [%track artist%' — ']%title%
Here is a sample Playlist Viewer grouping scheme you can try using...//======================================================================
// IF CD DISC, DISPLAY LIKE THIS ...
// ELSE IF NETWORK STREAM (Online Radio , etc), DISPLAY LIKE THIS ...
// ELSE IF FILE, DISPLAY LIKE THIS ...
//======================================================================
//----- (A) LINES SPLIT FOR EASY VIEWING OF CODE SECTIONS
$if($strstr(%path%,'cdda:'),
CD DISC' '$directory_path(%path%)
,
$if($strstr(%path%,'http:'),
NETWORK STREAM[' '%title%][' '%genre%][' '$directory_path(%path%)]
,
$if2($trim(%album artist%),'%artist%')' ● '$if2($trim(%album%),'%album%')' '$if2('('$trim(%date%)')','(%date%)')' '$if2($trim(%genre%),'%genre%')' '$directory_path(%path%)
)
)
//----- (B) LINES JOINED
$if($strstr(%path%,'cdda:'),CD DISC' '$directory_path(%path%),$if($strstr(%path%,'http:'),NETWORK STREAM[' '%title%][' '%genre%][' '$directory_path(%path%)],$if2($trim(%album artist%),'%artist%')' ● '$if2($trim(%album%),'%album%')' '$if2('('$trim(%date%)')','(%date%)')' '$if2($trim(%genre%),'%genre%')' '$directory_path(%path%)))