Lyric discussion by albie 

Cover art for 100,000 Fireflies lyrics by Magnetic Fields, The

“I have a mandolin. I play it all night long. It makes me want to kill myself.”

These lines are about projecting feelings onto music. You want to kill yourself anyway, but when you play your sorrows out on the mandolin, you can blame them on the instrument, the instrument in your arms (where your lover isn't). It's a way of feeling in control.

Negative
Subjective
Sadness
Projection
Music
Control
Sorrow
Instrument