Music with words is a distraction to your brain to perform a fully concentrated task. And Many research has proven that well-structured music helps a person to concentrate on one''s task.
Well-structured music without lyrics? Yes, Classical Music!
In this app, the specific classical pieces that are good for concentration were selected through the research on Baroque effect, Mozart effect, and etc.
Though, when you perform complex mental task, such as math, absolute silence is better for concentration.