An in-line sound module for a modular stack light system provides electrical and mechanical connectors to allow it to be placed anywhere in the stack. Axial orientation of the audio transducer and a flexible jumpering system allow preservation of central connectors between modules. In-line configuration permits multiple sound modules to be used in a stack light and to be teamed with different beacon modules. In one embodiment the in-line sound module may also include lamps to provide beacon functionality.