DMcG:

There is some information in the mudcat FAQ on formats you can use when posting or otherwise submitting songs to DT. I would suggest looking through it, since of course the most important exchange of notation any of us might do is with DT. The gist of this is ---- IT'S MAGIC. Actually, the requirements are pretty simple, we just don't know what incantations are used to turn the crap we send in into something useful.

Nearly all notation programs are either midi-based, or are compatible with and import/export midi. While it is fairly easy to see that a given notation program does an excellent or mediocre job of printing text, it is a little more difficult to see directly that the same levels of quality apply to the midi files that they produce.

Files that you are seeing that do not contain key and time signature information were probably produced by a simple (cheap?) program that does not enter this information in the midi file. Another possibility is that you are opening them in a simple program that does not "read" and use all of the midi information that is in the file.

A midi file CAN contain about as much information as you (and your program of the moment) are willing and able to put into it. All a midi file MUST contain is a time base (which can be a default) and "turn on note" and "turn off note" lists.

Requirements for notation depend on your own individual needs. Most "scores" are quite difficult to exchange electronically, since it almost requires that both sender and recipient have the same program. For certain purposes, this is not a large problem, since groups of users may generally have a program in common. This is somewhat the situation at mudcat, since NoteWorthy, ABC, etc are fairly widely used.

Wave, MP3, and other audio files are quite portable through ftp exchanges, but are of little use for places where you want to "post" something. It should also be noted that these files can be HUGE. Sending them as email attachments can easily run afoul of size limits imposed by email servers - and some servers do not permit any attachments.
While there are devices for "translating" "digitized and/or analog audio" to "coded" formats like midi, real people cannot afford them, and for the most part they don't work very well (for any routine uses, at least).

For postings, the ABC system works fairly well. The file that is transmitted is in "plain text," and anyone who wants to can open them, even if they only use the "trial version" and don't register the downloaded program (naughty, but it can be done.)

The same can be said for the MID2TXT/TXT2MID programs. Again, a text "string" contains all the information from the midi file, and can be posted almost anywhere, including IN an email. The receiving person(s) can run the text thru TXT2MID and get back a midi file. ALMOST any notation program will open the midi file as a "score," although what it looks like will depend on what software they use to open it.

A few web sites are posting scores in PDF format. This is a "GOOD THING," since the reader is free, and it is easy to download and print these kinds of scores. Unfortunately, the program to MAKE pdf files is fairly expensive. A pdf file is plain text, and in principle could be posted as text anywhere, or pasted into an email. The problem here is that the pdf (or the related eps) file for a half page of music will generally run about 70 to 75 pages of "plain text." ANYTHING that can be printed can be included in a pdf, and the "printout" that you get depends only on the quality of your printer.

For the present, the most "portable" file is probably midi. The files are quite small, and the format is universally consistent. Where attachments are acceptable, a midi file can be attached to an email.

For postings, the MID2TXT and ABC are about the only things useable now. Using MID2TXT, and referring people to the source for the programs, you can, in effect, send anyone a midi file - as text. Once they have converted it back to midi, they can play it and their own scoring program can ALMOST certainly make a printable score.

ABC and MID2TXT sites have been posted frequently, so I'll omit them here. A site for the full midi file specification has also been posted. If you have trouble finding any of them, come back here and I, or whoever beats me to it, will try to steer you to what you need.

John