they are called "angels"
There is no free, legal source for backing tracks, but you can have backing tracks custom made from many producers at a reasonable fee.
upper backing pocket
Backing soda is NaHCO3.
The person who is backing out of the parking space
Producers
I would say probably the person backing out, as they should of looked for any oncoming cars before backing out. ---- The person backing out of the driveway who did not yield to oncoming traffic.
Many Pink backing tracks are available on iTunes.
the backing group were called "Legend"
The person backing out. If you were in the lane/road behind them they needed to use caution when backing out.
producers
produce!
All plants are producers and the only producers in a desert.