The only way to get a user's Music folder is by parsing the iTunes Music Library.xml file. The following script does that and opens the Music folder, no matter where it is.

Hopefully.

I'm curious if it doesn't work. It's part of a larger (freeware!) project I'm working on. If anyone is interested, just copy and paste the code below into Script Editor, and Run. Code should wrap correctly in the clipboard. You can save it as a compiled script in iTunes Scripts folder if you like. Post your results and/or coding suggestions in this thread. Thanks!

tell application "Finder"
set xmlPath to (file "iTunes Music Library.xml" of ?
folder "iTunes" of folder "Music" of home) as alias
end tell
copy (open for access xmlPath) to fR
copy (read fR for 600) to x
close access fR

-- parse what we got from the xml file
repeat with thisL in (every paragraph of x)
if thisL contains ">Music Folder<" then exit repeat
end repeat
-- follow the progress of thisL
(*
set thisL to last item of my TextToList(thisL, "<string>file://localhost/Volumes/")
set thisL to first item of my TextToList(thisL, "</string>")
set thisL to POSIX path of thisL
set myMF to (characters 2 thru -1 of thisL)
*)
set myMF to (characters 2 thru -1 of ?
(POSIX path of (first item of my TextToList((last item of my ?
TextToList(thisL, "<string>file://localhost/Volumes/")), "</string>")))) as string
tell application "Finder"
open folder myMF
activate
end tell
--
on TextToList(theText, theDelimiter)
set saveDelim to AppleScript's text item delimiters
try
set AppleScript's text item delimiters to {theDelimiter}
set theList to every text item of theText
on error errStr number errNum
set AppleScript's text item delimiters to saveDelim
error errStr number errNum
end try
set AppleScript's text item delimiters to saveDelim
return (theList)
end TextToList