Like pretty much every song on Elliott Smith’s self-titled 1995 album, ‘Single File’ is about heroin. Or at least it is using heroin as both a subject and a metaphor.
In this case, the lyrics describe a visit to a methadone clinic, where you wait in a “single file” line to receive your treatment for heroin addiction.
Does that line also symbolize the dehumanizing march toward conformity, or death?
As with all great art, your interpretation is as good as mine.
Here in line where stupid shit collides
With dying shooting stars
All we got to show what we really are
Is the same kind of scars
And looking at you all I see is
You’re waiting for something
[Chorus]
Single file
You’re a murder mile
You idiot kid
Your arm’s got a death in it
[Verse 2]
If you’re choking up, take this paper cup
But there’s a price that you’ll pay
For trying hard to become whatever they are
And saying whatever they say
So help yourself to this bitter pill
Or somebody else will
[Chorus]
Single file
You’re a murder mile
You idiot kid
Your arm’s got a death in it
Single file
Single file
Single file
Single file
Meet Me In Montauk 
Well, I think to the extent he equates the line at the clinic to conformity, both concepts are enveloped.
Yes