The instrument that has come to be called the ``American'' reed organ shares with its relatives the accordion, concertina, and harmonica the use of free reeds, but differs from its reed organ cousin, the harmonium, in the use of a vacuum exhauster rather than a pressure bellows to drive the reed vibration. The acoustical properties of the instrument are summarized along with the results of some recent experimental studies. These investigations have explored variations in properties of both the reed vibration and the resulting sound as a function of pressure. Effects of airflow rate, and reed cell dimensions have also been studied. Both live and recorded musical examples are provided.