There are 4 bands called Mouth:

1) Mouth, Brighton, UK
The following description is for Mouth, the solo electronica/grind/noise-rock artist from Brighton, England. Starting in 1997 and still active now, Mouth's sound can range from the glitchscapes of Autechre to the brutality of Agoraphobic Nosebleed, the harsh noise blanket of Merzbow to the stoner rifforama of The Melvins.
The artist behind Mouth also plays in Brighton hardcore outfit With Scissors and noise-rockers Motorbikes.
The free album "2002-2005 Old Fucking Loud" is available to download from here.

2) Mouth, Hobart, Australia
This artist description concerns the Tasmanian punk band Mouth who formed in 1991 and disbanded in 1995. Consisting of Tim Evans (later of Sea Scouts and Bird Blobs), Cameron Stopps and Paul Evans. Forming in Hobart, Australia, Mouth took the energy and ethics of Fugazi (who themselves claimed to be big fans) and made music of razorwire guitar (no top E-string needed), violent bass and solid drums over which Tim Evans screamed teeth-cutting punk poetics concerning Homophobia, feminism, ageism, social rights and psychological theory, delivering these songs with such rightous energy as to kickstart a minor revolution.
Releasing the rapidly-sold-out cassette-only "Mouth" in 1992 and "jaw-droppingly intense" CD Victim Chant in early 1994 (released on Destroyer Records, and re-released in 2005 on Solar Sonar/Shock Records) which continues to convert listeners in increasing numbers Mouth continued to shock audiences live, where they truly shone. While the songs stand up on CD, there was no escaping the power of Tim Evans, 6-foot-something and with a a red, spiked crown of hair screaming with an unforced intensity about social injustices.
Tim Evans' characteristic DIY-mentality saw a slow start come to a premature end once relocating to Melbourne and turning down label interest. After disbanding, Stopps joined Little Ugly Girls, Tim Evans began Sea Scouts and Paul Evans returned to the birthplace of he and his brother, Railton, Tasmania.

3) Mouth, Chico, USA
Mouth wants to pursue art without contrivance or conformity, to fuse truth and beauty, to be a voice which helps the church truly be the church, to love people and form relationships, to live meaningfully and intentionally as a band. Mouth wants to do a lot of other things as well.

4) Mouth, Stockholm, Sweden
Consisting of Fredrik Joelson (Vocals, Guitar), Hans Carlsson (Guitar, Vocals), Peter Bohman (Bass) and Bengt Söderberg (Drums). Playing a very melodic punky rock, inspired by the Pixies. Released an EP and then the full length ''Hole of Your Head'' in 1995. Toured in Sweden and later in the US. Moved to New York only to disband and forming other projects, among them ''Binger The Voyager'', ''Hab''...