Hi Myst. To explain, when we post lyrics to a thread, in the line that says Subject:, you can modify that so the part that says RE: would be changed by the poster to say Lyr Add:.
This way those people designated to search the forum for new additions can locate all Messages which have "Lyr Add:" in the subject line.
To explain the Mudcat, it consists of two parts, the message forum which you are using, plus a database of songs which has been around for roughly 20 years, called the Digital Tradition. There is a link that tells you about Mudcat/DT history up top in the Links section.