Apparently Midvalley was a killer long before he became part of the Gung Ho Guns. In the past, he was part of a small band of jazz musicians that doubled as killers for hire. One day, after killing an entire bar full of people to get their target, Midvalley and his band were greeted by Knives, who proclaimed he was thoroughly impressed with their methods. Midvalley was cautious of Knives, but his comrades were not and tried to kill him for witnessing what they'd done. Knives butchered them in mere seconds however, and took Midvalley on as a member of his Gung Ho Guns.
Midvalley the Hornfreak was created by Yasuhiro Nightow for his Trigun series.
Major Story Arcs
Midvalley was among those Gung Ho Guns that witnessed Knives' second coming, he was also there when Legato was crippled by Knives, as well as when Vash made a huge crater in the moon.
Return of the Blue Wind of Death
Two years after this, Midvalley, along with Gray the Ninelives, Hoppered the Gauntlet, and Legato, crushed an entire police task force that had come to apprehend them. With the use of his sonic attacks, Midvalley made short work of many of the soldiers, after which Legato used his powers to crush the remaining soldiers together inside a container.
Resume Our Business
Afterwards, Midvalley was invited by Legato to the meeting of the Gung Ho Guns, along with Gray, Hoppered, Rai-Dei the Blade, Zazie the Beast, and Leonof the Puppet-Master. Having seen the power of Vash, he began complaining to Legato how they should defend humanity from beings like Vash and Knives, even going so far as to threatening Legato. This proved to be a huge mistake however, as Legato nearly broke Midvalley in half with his powers as a warning. Legato then explained their new objective: to make Vash suffer and destroy the image of humanity he'd made for himself.
Bottom of the Dark
During their journey to confront Vash, Hoppered conversed with Midvalley over their place in the plans of Knives, and how win or lose against Vash, they probably wouldn't be much use to Knives soon. Hoppered was okay with this however, as he saw his only purpose in life to be getting revenge upon Vash, even asking Midvalley to wipe away all traces of him after their task was done, provided he survived. Midvalley reluctantly agreed, sympathizing with how Hoppered had resigned himself to his fate.
Den of Thieves
Midvalley and Hoppered later met with Zazie the Beast at Dragon's Nest Mountain after he'd kidnapped Meryl. With Meryl as bait, the three Gung Ho Guns lured Vash and Wolfwood, as well as Milly who'd tagged along for Meryl's sake, to the mountain and right into their ambush.
Crying Wild Bullet
Hoppered quickly split up Vash and Wolfwood, leaving Vash for himself and Wolfwood for Midvalley, who immediately used his "Ultra Shock Sonic Web" on him, incapacitating him so that he couldn't interfere with Hoppered's battle against Vash. To Midvalley's suprise, Wolfwood quickly woke up, and used his rocket launcher to try and blow Hoppered away, while also nearly scorching off half of Midvalley's face, making Midvalley realize that he'd better not underestimate Wolfwood as he was a Gung Ho Gun just like him. Midvalley was unable to counterattack however as his saxophone was damaged, and so he slipped away to repair it.
The City, and Then the Banquet of the Dogs
Midvalley then met up with Hoppered, who'd momentarily postponed his fight with Vash, and together they ganged up on Zazie to prevent him from reporting to Legato or Knives of their plan to actually kill Vash rather than make him suffer. Using his mastery of sound, Midvalley neutralized the sound of Hoppered's attack, allowing him to sneak up on Zazie and kill him.
As Vash was making his way towards Meryl, Midvalley and Hoppered planned to use the same technique they'd used on Zazie to try and kill Vash in one shot, but Wolfwood and Milly managed to disrupt Midvalley's sound-dampening just before Hoppered was able to collide with Vash at full force, resulting in another face off between Midvalley and Wolfwood.
Midvalley hoped that attacking Milly would distract Wolfwood and give him an opening, but Wolfwood managed to defend her and himself even with his eyesight still on the fritz from Midvalley's initial attack, and so Midvalley slipped away once again.
Unable to beat Vash, Hoppered set off several explosives he'd planted in the area as a last resort. Vash was able to absorb the blast however, allowing everyone to survive. Midvalley then approached Hoppered to kill him as per their agreement, but Wolfwood, with his eyesight now fully returned, interrupted him in order to finish their fight. They were in turn interrupted by Legato however, who came to retrieve Hoppered and Midvalley. Unwilling to abide by Legato's orders and let Vash live, Midvalley tried to kill him, only to be shot and killed by a Legato-controlled Hoppered.
Legato then crushed Midvalley's body beneath his bike for good measure, and later uses his powers to force Midvalley's dead body to kill Hoppered for his betrayal.
Let us Walk the Path to Redemption
Vash however is able to shield Hoppered from Midvalley's attacks, and Legato is soon afterwards forcibly extracted by Elendira the Crimsonnail, the "lost number" thirteen of the Gung Ho Guns. Hoppered eventually passes away due to his injuries though, and Midvalley is buried beside him with his saxophone hung on his tombstone.
Powers and Abilities
Midvalley is a musician with impressive skill in playing his saxophone, Sylvia, with which he is able synchronize sound waves with pain receptors in the human body, causing immense physical damage, and even killing. He is also capable of neutralizing sounds by playing counter-frequencies, creating absolute silence.
Although he primarily makes use of his sound-based attacks, Midvalley is also a skilled gunman. His saxophone has a hidden gun built into it, and he also carries some more conventional pistols with him.
In the anime, Midvalley is much more loyal to Legato, acting as his bodyguard, as well as leading the Gung Ho Guns under his orders. He ends up being killed in a confrontation with Vash, who shot his saxophone to disable it, after which Midvalley tried to use his sax's built-in machine gun, only for it to explode and kill him due to the damage it had sustained.