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I've got a selection of practice mutes including the Artino (metal inside, rubber outside, very heavy) which I used to like most, but not so much nowadays. The best seems to be the USA-made Ultra brand, although it's not as heavy as others - random ones I bought from China for pennies. (I used to assume, the heavier the better, but it doesn't seem to work that way)
But I recently bought a selection of orchestral rubber mutes (Tourte 2-string and 1-string versions), and initially they don't seem to attenuate any less than the so-called practice mutes. Again, the good American ones are probably made of slightly softer rubber and this helps them stay on the bridge and not slip off.
I've also got a solid mahogany mute which is a very beautiful object and gives a distinctive beautiful delicate tone but, because it's inflexible, will probably be useless in an orchestra (and it's very sensitive to bridge thickness), and the ones that stay behind your bridge are so much more convenient.
I should have done a fuller appraisal before posting this, I guess. I'd like to hear from you regular orchestral players about what you have used, and what works under fire and what doesn't (lol). Probably in a big group of players it doesn't matter, as everyone gets lost in the mix!
I normally use a basic round Tourte 2-string mute. It gets the job done, but it tends to rattle slightly on the afterlength, so I remove it completely if I know I'm not going to need it before I have a chance to get back to my case.
Once, when I forgot to put the mute back on my viola during a concert intermission, I used the famous/infamous "$1 mute": a dollar bill folded into a thin strip and placed through the strings on the afterlength, and pushed up against the bridge when needed to mute the instrument. It worked surprisingly well, and had a nice velvety sound that I don't really get from the Tourte mute, though you have to really jam it against the bridge for it to work properly. It also shouldn't be used regularly because, if you're not careful with it, you may cause your bridge to start leaning or even knock your bridge over.
I'm planning to buy an Alpine Shield mute, which I've heard good things about from professionals in my area (it doesn't rattle on the afterlength) though I will most likely wait and combine it with my next string order to avoid paying extra for shipping. The Finissima mute similarly avoids rattling, but isn't wide enough to fit on a viola.
I thought those little round tortes that attach onto two strings below the bridge were orchestral mutes and really just dampen a couple strings as the conductor needs it, not actual practice mutes.
Although Tourtes only fix onto two strings (some of them only one string), they actually dampen the bridge, so all 4 strings, not just the strings they are sitting on. In theory they are "orchestral" mutes, but you can use them for practice, unless your neighbours are very sensitive to sound. Some people are disappointed at how little any mute mutes. The name is misleading really. Otoh, you don't expect a trumpet's mute to make a trumpet nearly silent, lol.
I do have one of the tortes on my violin. I bought it thinking it was a mute mute. Does not mute like a practice mute. Then it was explained to me.
I find it does mute like a practice mute, but I'm going on my memory of what practice mutes sound like, so I could be wrong.
I use my Tourte for practice. Works great when I don't really need to mute my violin, but want to spare my ear under practice. It works pretty much as well as my Ultra, maybe a slightly less muting. But it works for my use and it's easier to put on. When I need to mute my violin I use my ebony or brass mute.
'Armed with theory, practice becomes meaningful. Through practice, theory becomes fulfilled.' - Egon von Neindorff.
The solution may be the violin-shaped 1-hole tourte which my teacher, a violist, uses - the 2-string has big round holes: the 1-string version has a narrow slot that tapers to a point and can be pressed onto the string. An interesting experiment might be to have one on the E string and one on the G string?!