This version prompts for the source file and creates a new file on your desktop named Music_Export.txt that contains the original source except the track title has been changed as specified in the posts above.
set theXMLfile to (choose file) as string
set theXML to paragraphs of (read file theXMLfile)
repeat with i from 1 to count theXML
if item i of theXML contains "<track_title>" then
set tt to item i of theXML
set tt_o to offset of ">" in tt
set tht to item (i + 2) of theXML
set tht_ws to offset of "<" in tht
set tht_o to offset of ">" in tht
set tht_string to text (tht_o + 1) through -(tht_o - tht_ws + 3) of tht
set new_tt to (text 1 through tt_o of tt) & tht_string & ". " & (text (tt_o + 1) through -1 of tt)
set item i of theXML to new_tt
end if
end repeat
set newXML to theXML as string
set deskPath to (path to desktop) as Unicode text
set filePath to deskPath & "Music_Export.txt"
try
close access file filePath
end try
set fileRef to (open for access file filePath with write permission)
set eof fileRef to 0
write newXML to fileRef
close access fileRef
X 2