The techniques used in the short film are live-action (in the scenes where the characters' torsos appear), stop-motion with plasticine (in the scenes where the characters' heads appear), and PS1-style 3D (in the scenes where the characters sing).
Jack Stauber (the director of this short) voices every character and sings every song.
You can hear a girl crying in the song "Crying."
Despite being a smoker and presumably having the worst lung power, the Grandfather's song ("Easy to Breathe") is the longest non-instrumental song in the short.