Jack Stebbins can harmonize with himself while whistling. Here he does the theme song from the Andy Griffith Show and a Beethoven oboe duet.
He's crying because he can actually kinda hear his own music through the power of 21st-century headphone technology.
Beethoven's Fifth Symphony, illustrated with audio editing software. Great for people who can't read musical notation or want to pretend they're playing Conductor Hero.
Let's settle this once and for all...
The word "/mu/sicians" in the second panel is a reference to the music board on 4chan. Credit where credit is due!