WARNING: I am going to be preachy. Sorry about that. But I see so many people come here asking how to implement an idea they have without describing or even mentioning the problem they are trying to solve. It is very frustrating.
I'm pretty much a noob in the expression language/tag editing area, so I could be missing something important.
Well, everybody has to learn, but your first lesson is don't even consider changing the [Track #] field in MC to letters. It would break so many things (probably including the Mercedes-Benz COMAND system) and simply is not required.
The second lesson is that when you have a problem with MC, come here and ask for help with the problem. Don't ask how to implement the solution you have decided upon, because it may be a bad idea.
I don't think this issue has anything to do with Gracenote, which would just be used to look up additional metadata, maybe images if they aren't stored in the file. The play sequence is going to be based on either the file name within the Album you select, or the track number sequence within the Album, or much less likely but possible, the track name within the album. The last one is what you are trying to avoid, and would be silly for MB to do. Everyone knows that the track name isn't the correct play sequence. If you are asking MB for help, ask them how to fix your sort problem, not how to turn off Gracenote, because they will think you want to save download data, or something else.
I suspect that COMAND does expect a certain folder structure as well to read track information. Probably \[Artist]\[Album]\ then track files. That thought seems to be supported by this thread:
http://www.glaowners.com/forum/electronics-audio-lighting/5282-how-use-album-art-playlists-sd-card-likely-usb-sticks-long.html Unfortunately the thread doesn't really discuss sort sequence.
So, the [Track #] field is numeric, in fact an integer as mentioned above, and it is sorted numerically. so 1, 2, 10, 11, 12, etc. If you enter "01" into the field, it will be correctly saved as "1". So this is correct;
I can see how this expression will change how the track number is presented in JRiver, but it doesn't look like this will actually change the track # tag in the file. If I use a plain old tag editor and type in "01" in the track number field, it just reverts to 1.
This won't change anything (sorry RD);
In Media Center, you can modify the tags by using "=PadNumber([Track #], 2)" in the Track # field
The [Name] field in MC should just contain the track name, and nothing else. Unless of course, MB is doing the silly thing, and sorting by track [Name]. That can be fixed, but you need to confirm that if the method below doesn't work.
Those two fields are primary fields for all sorts of stuff, like metadata lookup, and would be expected to be accurate by any player that you use to play them. So some players will read the metadata in tags, and some will just use the file name and parse out what they think the metadata should be.
You mentioned
I'm doing battle with Mercedes-Benz COMAND music interface. It does not respect track numbers when it plays an album. For example, if I don't have [Track] - [Title] it just plays songs in the alphabetical order of the titles in the filenames. With [Track] - [Title], the order of play is 01 - First Song, 10 - Tenth Song, 11 - Eleventh Song, 2 - Second Song, etc.
So this tells me that COMAND is likely to be sorting by file name. That may be a setting you can change. That is worth asking MB, but you can solve your issue all by yourself. Also, the sort/play sequence probably depends on whether you select tracks by "Current Track List", Tracks, Playlists, Artists, or Albums, all of which can be selected in COMAND.
It looks like you have renamed the files correctly already, but did you use the "Rename, Move, & Copy Files" function? I think that is what you mean by;
I have used the JRiver 'macro' to rename the filenames using [Track #] - [Title]. Looking at the filename created by that the filename has a leading zero for 01.
If you haven't, have a read the
Rename, Move, & Copy Files Wiki topic, and understand what it does. It is a very powerful tool. BTW the correct naming convention for renaming the files is "[Track #] - [Name]", but I think that is what you meant.
Now when you do this;
When I pick an album via "Folder", the tracklist is in the right order and the song names have the leading "a".
I think COMAND is sorting by file name wthin the folder you selected. That makes perfect sense to me. You are selecting by the file location in folders, so COMAND sorts by folder/file name.
When you do this;
If I manually change a few filenames to "a - First Song" etc, they still play in the same demented order when selected by "Artist" or "Album" in their media system, but the song names don't have the leading "a". So it is finding the correct Title metadata either in the file or from Gracenote.
You are selecting tracks to play by their metadata, specifically [Artist] or [Album], or a combination of both. I would expect COMAND to sort by [Track #] under in this case. If it isn't,
then check if Shuffle is turned on for playback, and if it isn't, are you able to check the playback sequence that tracks will be played? That may give you a hint as to how COMAND is sorting the tracks.
Ultimately though, it looks to me like COMAND uses the same convention as all other players, and expects the same folder, file naming, and metadata formats as other players. If COMAND continues to play in a demented sequence, that is definitely a question for MB... once you get your metadata, folder structure and file naming worked out in MC and on the memory card you are using.