Impractical Musical Instrument Skills

Cool but Inefficient ways of playing instruments. Whether by an unusual posture or position.

Anime and Manga

Tayuya in Naruto plays her flute to control three giants she invokes (they move according to the position of her fingers). How she can very precisely control these three bodies separately to track her opponent, and still play a coherent melody is a wonder.
Brook from One Piece claims to be proficient at any instrument; so far, we've seen him play Violin, Piano, and Electric Guitar. On the one hand, he has had fifty years by himself on a ship full of instruments to perfect his skills; on the other, you'd think having no flesh on your fingertips would, at the very least, make it hard to properly fret a guitar without a lot of extraneous noise...

Film

In the film version of Amadeus, Mozart plays the harpsichord upside down, crossing his arms so his hands can be on the proper side.
- In the Simpsons version of the same story, Mozart (Bart) plays with his feet and his butt. Not at the same time.

Literature

A line from Nanny Ogg has it that all her family are musical in some way. Including "her Shawn" being able to fart Lancre's national anthem.

Live Action TV

In Black Books, Manny sits at a piano and plays a complex classical piece he heard on the radio seconds before. He can play any piece of music he tries, even when hiding underneath the piano and using spoons to strike the strings.
In Red Dwarf, Lister is a terrible guitarist, but thinks he's another Jimmy Hendrix. Starbug gets stuck in an area inhabited by mind-reading GELFs, and Lister has to go out to make repairs. The crew get two Listers back, and not knowing which is which, test them both on aspects of Lister's life and personality. They give one of the Listers his guitar and tell him to play - it's awesome, because the real Lister thinks he has Implausible Musical Skills with a guitar, so they shoot him.

Newspaper Comics

In Peanuts, Shroeder is able to play symphonies by Beethoven and others on a toy piano with painted-on black keys. This is Lampshaded on several occasions.

Western Animation

Looney Tunes: there's one cartoon in which Bugs Bunny plays the piano by literally hopping on the keys (as a rabbit, you really don't see him doing that much). He also plays it like a typewriter, complete with a margin bell and hand-returned carriage. Still another scene has him picking up piano keys and then dropping them back into place, producing music all along.
In the short "What's Up Doc", a toddler Bugs plays a concert-quality piece on a toy piano; shades of Schroeder.
In more than one Tom and Jerry short in which Tom played the piano ("Johann Mouse", "The Cat Concerto"), he did it with his toes while using hands to try to catch Jerry. In "The Cat Concerto", Jerry also played the piano by plucking out two of the hammers and playing directly on the strings.
In an episode of Futurama featuring the Beastie Boys, because of them being heads in jars, one of them scratches a record with his tongue.
In Phineas and Ferb Perry the Platypus does an Homage, playing Dr. Doof's guitar behind his back.

Real Life

Jimi Hendrix playing with his teeth and tongue.
Some turntablists are known to turn around and scratch (records, of course) behind their backs, scratch with their elbows and shoulders, and pick up the tables by straps and hold them like guitars.
And, of course, there are people who can play all the parts of a certain song on one instrument. It gets pretty mind-blowing.
Jerry Lee Lewis used to play the piano in outrageous ways.
Two guys one guitar or the 4 hand exchange
Rashaan Roland Kirk played two saxophones at once, as well as practically every other brass or wind instrument individually.
- Kirk occasionally played a saxophone and a flute simultaneously. He played the sax with his mouth, and the flute with his nose.
Richard Hyung-Ki Joo plays the piano in numerous improbable ways in A Little Nightmare Music. These include playing while lying down under the piano, head directly under the keys (as if he was a garage mechanic under a car) and playing the strings with a dental drill. His partner, Aleksey Igudesman, plays the violin in similarly fantastic manners, such as playing while Riverdancing.
The French Vaudeville performer Le Pétomane, whose entire act consisted of farting musically onstage.
Little Richard used to play the piano with one leg up on top of it.
George Formby was famous in Britain in the 1930s and 40s for singing silly comic songs and playing the ukulele (technically a banjelele, since it had a banjo-style resonator). A recent documentary highlighted his incredibly rapid and precise playing, which has sometimes been ignored in view of the fact that he didn't play "serious" music.
Michaelangelo Batio is an ambidextrous guitarist known for playing guitars with both hands, at the same time!
Django Reinhart, one of the greatest jazz guitarist, with only two complete fingers.
Rob Kleiner of Tub Ring will often jump on his keyboard stand and continue to play.
Jazz saxophonist Lester Young was famous for holding his saxophone at incredibly unnatural angles while he played.