Parking Lot Philharmonic

[Quicksilver]

The sun beams at me
A far-off candle’s spotlight seen
Via gradient of eyelid veins
I am still
Breathing in silence, expectant  "still/breathing" is nice
An afternoon’s overture begins to rise  reference to afternoon is puzzling, looking forward to "First of the day" later (This is a result of anxiety making the morning difficult, but that is not communicated clearly, good catch!)
Car horns blare in opening
Wood winds play with flame-bright leaves
A snare drum rallentando of stranger’s steps  the steps are slowing... why? (the person is approaching their vehicle, but it doesn't communicate well in the moment)
The orchestra sits as audience
Performance in the round reversed
I am on stage, in spotlight center
My nerves vibrate slowly, tugged by the breeze
A melodious harp of my own sinew
Harmonizes with muscles to ease their grip  an interesting conceit - hearer as ground zero of the performance
A loosened breath
First of the day  see above vs. afternoon, is this a new day?i will add a line to clarify I think
A note in a symphonic swell
Then

burbled

electronic trills.

A notification from my responsible self  cell phone...
I return to the shade of the building  ...so he can see the display
My fingers seek a warm portion of my pocket
Remaining heat from sunlight  perhaps "Retaining" but this is fine, too
Clings to the leather of my coat
As a folded program, or ticket stub  the warm spot is the memento
A reminder of peace
I find it, and hold it
Long after I can recall the tune  ok, there are two points in time here, humming and not recalling.  Too much present tense?
I find myself humming
Without knowing why

In mild critique, this is evocative and suitably dreamy.  As noted above, I have some trouble with the time sequence of events (even thoughts and emotions are linear that way).  As a matter of style, you don't over-use "the" as some do but you might seek alternatives to "A" especially at line beginnings.  Are there places where "A" can be omitted, replaced with further descriptive words  (e.g. "paper reminder of peace")?  Parallelisms have their place, but so has variety.

The title (unless it refers to a particular song, group, or concert) is a little opaque (g).  Thoughts are like that, and sunlight fits, too.  But there's no firm connection to the body of the poem otherwise - or I'm just missing it.  The rest of the metaphors are musical... perhaps the title could be, too?

Definitely get the feedback, thank you! The title was something that came up very early in writing this one, so once the musical focus emerged, it didn't really fit anymore. I'll think through a few, but for now, I'll try:
Parking Lot Philharmonic
The sun beams at me
A far-off candle’s spotlight seen
Via gradient of eyelid veins
I am still
Breathing in silence, expectant 
An afternoon’s overture begins to rise  
Car horn's blare in opening
Wood winds play with flame-bright leaves
Fading snare drum rallentando of stranger’s steps
Into bass boom of closing car doors
The orchestra sits as audience
Performance in the round reversed
I am on stage, in spotlight center
My nerves vibrate slowly, tugged by the breeze
Delicately floating notes,
A melodious harp of my own sinew
Harmonizes with muscles to ease their grip
Releasing morning's tension in an at-peace breath
First of the day 
The root note in a symphonic swell
Then

burbled

electronic trills.

A notification from my responsible self 
I return to the shade of the building
My fingers seek a warm portion of my pocket
Receding heat from sunlight  
Tenuously clings to the leather of my coat
As a folded program, or ticket stub  
Paper scrap reminders of peace
I find it, and hold it
Moving the melody to deeper places
Bracing for future, dreary days to come
When the tune is lost to time
I will find myself humming, cheerily
Without knowing why