White Shirt Sleeves

Apologies for the fuzzy photo. I would have loved to have gotten a closer view of this man's partly rolled up shirt sleeves. He is singing in a band at a public community concert. Notice the "V" shaped area under his arm directly above the folds of his sleeves? I do and I really like seeing it. I also imagine what this sleeve would look like buttoned neatly about his wrists or hanging lose.