The methodical and precise sound of a sewing machine is oddly calming.
It is one of those steps that looks as if it can be done in an auto-pilot state of mind. But it is actually a job requiring incredibly skill and a deep knowledge of the machine and its relationship to the person. In order to perfectly sew a bag, one must know the machine's personality - its strengths, weaknesses, and quirks.
Perhaps it is this level of intimacy - a result of such precision and perfection along with the constant uniformity of the sound - that makes it so calming: