Yogi: Is the breath a samatha or vipassana object?
Sayadaw: Samatha idea is to use only 1 object, a conceptual object.
In vipassana practice, the object is nature/reality – and the awareness takes multiple objects, not only 1 object because the mind wants to know what is happening and the relationship between objects.
The breath becomes a samatha object when the mind pays attention to the concept, the direction of the breath – air going in and out. Direction is a conceptual object.
The breath is a vipassana object when we know both the mind and the object – the sensation and the awareness.
The awareness knows more objects when it becomes stronger. For example, if you use breath as the main object, you can know the awareness, breathing, thinking, feeling and sound at the same time when the awareness strengthens.