I do improvized couples dancing, and have experienced time slowing down. It is an unique kind of experience, not just a different conceptualization of an everyday experience.
Buddhists say that you are where your attention is. So if a sound captures 100% of my attention, I am that sound. This feels strange on the surface, but when you look deeper into it, it reveals deep wisdom about the human experience.
In my understanding, it is possible, through years of practice (meditation etc.), to learn to direct your attention. Most of us have very limited capability to direct our attention, because we have not practiced it. Actually, modern life trains us to become less capable of directing our attention.
Based on your description, when you talk about "focusing on one task", you describe a flow state where you are 100% absorbed in the task. In a way you have not consciously decided to focus your attention. (I use a very specific meaning for the word conscious here, it is more aligned with the buddhist sense of the word, instead of western sense of having-thoughts-about the thing).
Your attention has been captured by the task at hand. In a way you are lucky that an useful and productive task has captured your attention.
In my understanding, if you learn to direct and hold the attention consciously, there is a next stage you can learn, where you become able to split your attention, to be conscious of two things at the same time.
If you direct some of your attention to the task at had, and some attention to a part in you observing yourself doing the task, then it feels as if the task is "happening", instead of you "doing" the task.
When this happens, there are effects on the physical experience as well, such as time slowing down. I have been blessed with such experiences when dancing, It seems to be possible to have such experiences also without being able to consistently and consciously direct the attention, as I have been blessed with such experiences in my dancing. But in this case it is accidental.