What happens to Siddhartha when he meditates in Siddhartha?
In the chapter entitled "Om," Siddharta is shown to spend a long time meditating on the loss of his son as he lives his life as the ferryman on the river. This process of meditation is shown to benefit him and to increase his understanding and empathy of other humans and of the lot of man. Note how the benefits of his meditation are described in this quote:
Within Siddharta there slowly grew and ripened the knowledge of what wisdom really was and the goal of his long seeking. It was nothing but a preparation of the soul, a capacity, a secret art of thinking, feeling and breathing thoughts of unity at every moment of life.
Meditation therefore is shown to be something that brings Siddharta closer to his goal of Enlightenment, even though it does little to soothe the pain of the loss of his son. Note the way that this process of meditation is described as a "preparation of the soul" that helps Siddharta become more aware of the unity of life and grows him slowly towards the "goal of his long seeking."