Integrate palm mute playback with palm mute lines

I'm pretty sure palm mute is possible, but can't verify right now.

See: https://musescore.org/en/node/293139 for a recent discussion on how to do palm mute.

This is what MuseScore does now, I'm just pointing out how to do it. I'm definitely not saying it's not a good idea to improve it. If you use the invisible or even non-visible text it works exactly like staccato except there's no shortcut possible at this time. You can apply it to several items at a time by ctrl+clicking each item you want to add to the list, just like staccato.

That voice bank switch is the method MuseScore usea and that one sound is the only one available in GM soundfonts.
Making that switch easier via a line seems a reasonable request, won't change the sound though

Also: https://musescore.org/en/node/239566

As someone who writes a lot of electric guitar parts, having a P.M. element which affects playback would also be near the top of my wishlist. Having some auditory feedback on it is essential to working out rhythm guitar parts. Take e.g. the opening of Summer of 69: Without the muting pattern, it's just constant 8th notes on the same chord, for 4 bars straight. Which notes are muted is often the single most important aspect to a riff, so it's really helpful to be able to hear whether I've put it in the score in the right places.
Like Teemu Kleinen, I would strongly prefer a implementation based on note-length/staccato. It's what I end up inserting manually most of the time, and IME it gives a workable outcome in any situation, right away, regardless of soundfont or patch. For clean electric guitar, switching to the muted channel does usually sound a tad better ("realistic" is impossible outside of dedicated guitar samplers with builtin amp sims & clever humanization control, anyway) - but for anything else it sounds distracting, if it's not downright unlistenable (distorted, acoustic, bass, banjo, ...).
I've tried to list the rest of my thoughts on implementation below.

Pro staccato:
- Arguably the most common way of rendering variable palm-mute in MIDI - see most tab software, or the Doom soundtrack)
- Long sections of uninterrupted P.M. (e.g. Every breath you take) is where the classic Muted Guitar patch from the Roland SC (which every GM soundfont tries to imitate) sees most its use. But I would never notate those by cluttering the score with one long dashed line that spans pages, anyway. Just announce it via staff text once (just like pizz. & arco for strings) - which is already easily doable in mscore, so no need to implement it as a dedicated feature.
- Very predictable, no sudden changes in sound. Always matches the base sound of the instrument, without any extra work.
- Goes nicely with playing back dead notes (more extreme muting that is purely percussive) as ultra-short - a feature I will probably request elsewhere ;)
- Leaves the possibility of continuously adjusting the degree of muting, via note length. Switching channels is binary.
- During arranging, I could copy&paste a rhythm guitar part to try out how it would sound e.g. if the organ played it instead. Obviously, a keyboardist cannot palm-mute, but the variation the guitarist achieves via muting or not muting different notes still transfers over somehow, instead of being lost completely (or switching back and forth between random keyboard channel patches...)

Pro channel switching:
- Often sounds better on clean electric guitar
- In theory, separating out the muted notes offers a bit more flexibility if I want to use the MIDI output from mscore in external software. But if the virtual instrument uses e.g. keyswitches or CC for controlling muting, instead of a seperate MIDI channel, I'm back to square one.

Just wanted to open a feature request for the same and found this issue. I'm a bit surprised though that some seem to prefer stakkato over an actual palm muted sound. So let me quickly chime in, but make a strong case for changing instrument channel:

• A Stakkato is not a palm mute, they're logically and practically two different things. That's why default guitar provided with MuseScore already defines a channel for palm mute, as the general MIDI spec also does.
• Switching channel produces more realistic playback results in my ears, as this score example clearly illustrates (where palm mute plus stakkato is used, which is even more realistic).
• OK, the current instrument banks provided with MuseScore only have an electric muted guitar (which to me is still a more tolerable change from acoustic sound than permanent stakkato), but future versions of MuseScore could ship with an updated default sound font to include muted acoustic and distorted guitars (or even banjo sounds for what it's worth ;) )
• You can have any muted sound you like as a channel already as of today. The sound font from Soundfonts4U (recently added to the soundfonts handbook page) already has a muted distorted guitar. Just update your instruments.xml, or change the < channel >< program value="52"/ >< /channel > in any musescore files itself to the instrument you want to sound for mute (btw you can also create new channels such as "fret noise", "harmonics", etc. this way). I believe it may even be possible to add an expression to your custom channel that does stakkatos, legatos, anything you like.
• If you check out the distorted muted sound from the SGMv2.01 package from the link above (yes, try it), it becomes clear that you will want to have a way to add articulations to a muted guitar sound (as you would vary pressure and articulation on a real guitar as well). If P.M. --- would automatically make everything sound as stakkatos, we're (a) effectively mixing up two things here (b) it would be really confusing that stakkato signs in such a section would seem like they don't do anything and thus (c) remove a feature instead of adding one.

One thing to leave you with: If the P.M. --- sign would be implemented as stakkato, but somebody wants to show the sign in the score, but not hear stakkato's and switch channel instead, how would one do that, would they be stuck with it?

Stakkatos can easily be applied to a group of notes by selecting the range and clicking the stakkato sign. Implementing the PM --- as a channel switch would still leave everyone with the option to right click on it and make it sound normal (or whatever sound you like, given the flexibility of MIDI i understand you could even setup your own stakkato sound via expessions), so channel switch implementation increases flexibilty, while stakkato implementation would take it away.