How are palm mutes shown on guitar sheet music?

I learned how to read off piano and thinking about looking up some nontab guitar pieces. I'm curious how they're shown. Are they just noted by how ever the composer wanted or is there some standard way.How are palm mutes shown on guitar sheet music?
Usually, it is with PM written below the chord/note (below the stave).








--x---


--x---


--x---


is usually hit the strings when your left hand is muting themHow are palm mutes shown on guitar sheet music?
Depends. What most have shown is a common palm mute notation, but sometimes you still want the note to sound (like in heavy metal use of a 'pedal note'... think earlier Metallica).





In those cases, the music is notated normally, tab or sheet, and just above the staff is will say 'P.M.' with an extended dotted line over the muted portion. This notation is typically used when you have a muted 'pedal note' but the rest of the notes (usually chords) will ring.
usually as xxxxxxxxxx's





in the timing of the piece, so whatever the length of the note is, with an x.
---x---


---x----


---x----





Or even INITIAL PM
I've seen them a few different ways, most noticibly just an X.