It is believed that free reed instruments originated in Asia and were subsequently introduced to the West, where eventually instruments such as the harmonica, accordion, and reed organ were developed. The reed organ enjoyed a period of great popularity in North America for about a century, beginning around 1835, with thousands of instruments per year being manufactured. The reed organ was introduced to Japan and also became successful there, with Japanese reed organ production beginning in the 1880s. The instrument often called the ``American'' reed organ differs from the ``European'' harmonium in the use of a vacuum exhauster rather than a pressure bellows to drive the free reed vibration. The reed organ does not use a resonating pipe, but reed cell dimensions and other characteristics of the reed environment as well as the shaping and scaling of the reeds, can modify the spectrum of the sound produced. Recent investigations have explored, in some detail, the variation of the frequency and amplitude of reed vibration as a function of blowing pressure.