I have had a play with my usb stick and mp3 filename formats. This is what I have discovered:
First, if you want the albums to be played in track number sequence then when you rip the cd to mp3 you need to have the MP3 tag for the track name begin with the track number (zero filled if 10 or more tracks per album ie 01_Track1, 02_track2 etc) otherwise it plays the tracks in Alphabetical order.
Second, if you want to use Playlists (ie m3u files containing lists of tracks to be played) then you must have no spaces in the file name, if you don’t use playlists then spaces in the filename is OK.
As to the structure of the files on the usb stick -
The head unit displays and the Album, Track title etc from the MP3 Tags in each file and not by the stored file / folder sequence on the stick, however, for my own preference I have individual folders per album, including multiple album folders per group
Group1
Album1
Track1 (MP3 track name 01_track1)
Track2 (MP3 track name 02_track2)
Track3 (MP3 track name 03_track3)…
Album2
Track1 (MP3 track name 01_track1)
Track2 (MP3 track name 02_track2)
Track3 (MP3 track name 03_track3)…
Group2
Album
Track1 (MP3 track name 01_track1)
Track2 (MP3 track name 02_track2)
Track3 (MP3 track name 03_track3)…
Group3
Album
Track1 (MP3 track name 01_track1)
Track2 (MP3 track name 02_track2)
Track3 (MP3 track name 03_track3)…
etc etc
If you already have lots of MP3’s without track number, you can use a freeware program called “mp3tag” to rename the track name to include track number - this is pretty easy.
To add the track number to the track title you run mp3tag.exe, open the folder containing the album, check it has track numbers in the details (if not you can add them manually) then select all the tracks and choose
convert tag-tag from the convert menu option.-
and
select Field = TITLE
Format String = $num(%track%,2)_%title%
I think there is a limit of 2000 to the number of tracks ber USB stick.