Dave's ESL Cafe's Student Discussion Forums

[tcom]

Dear Teachers.
Could you give me some advice on the meaning of the following sentences?
These sentences are from writings of a conductor who seems to be looking back on his days of the first recording experiences in the studio.

The sentences are as follows:
Then, here it was: one more time the great deep breath,
an appropriate downbeat, and I was launched among
friends into the best of all commercial worlds, where rehearsal was
a rare (and usually unnecessary) luxury.
Call the tune, read it down, wait for the sound booth's microphone adjustments,
talk with Ray on the phone for his reactions -- then,
silence -- watch for the light to come on: "Take One, SPEED!"
We're rolling. What a great and memorable music experience.

I want to know the meanings of "Call the tune", "read it down", "Take One, SPEED!" and "We're rolling."
First, Why does the part of the sentences lack the subject words?
Second, What does "Call the tune" mean? "to decide sth as one likes (idiomatically)"? Or "to say the name of the tune (literally)"?
Third, What is the meaning of "read it down"? Was he looking over the score and playing the tune?
Forth, What does "watch for the light to come on: "Take One, SPEED!"" describe? Particularly, What does "Take One, SPEED!" mean?
Last, What is the meaning of "We're rolling."? Were they playing the tune? Or, were they shouting for joy after already finishing the performance?
I cannot make a clear sense of these.
If you please, please show me the answers. I would be very much grateful.

[dabro]