An orchestra is defined as a large instrumental ensemble typical of classical music. An orchestra features bass, brass, strings, woodwinds, and percussions. In the list given above, the section that is not one of the four groups in the orchestral palette is the voices. The answer would be "voices".
The architectural feature of the Islamic artists that came from the Romans was the horseshoe arch. This is what they liked best in Roman culture, so they decided to use it in their art and architecture as well. Islamic architecture is quite different from any other, although it was certainly influenced by many other world architectures.
