The three Banu Musa brothers are almost indistinguishable and most of the information is at this link. However, there is some information specific to the second brother: Ahmed ibn Musa ibn Shakir.
He wrote one texts under his own name on mechanics On mechanics is a treatise on pneumatic devices. Another text on the theory of the balance was written by the three brother but probably Ahmad played the leading role.
Article by: J J O'Connor and E F Robertson