Typically there are 61 keys on a pump organ and about 122
reeds. However, there can be a much greater number of reeds.
The more banks of reeds you have the more sound variations you
can produce. This photo shows both the construction and various
sizes of reeds. Reeds are made of brass and, if kept clean, can
be made to look like gold (they'll also play a lot better). The
largest reeds are from the bass end and get progessively
smaller as they go up to the upper treble.
There are two parts to a reed, the case and the tongue. The
case and the tongue are aligned next to one another in a very
precise way. If they're off by just the slightest amount they
will produce no sound. The tongue is held tightly in place by
two brass rivets. When air is drawn between the case and tongue
a vibration is created and we have the sound of a note. These
reeds are in need of a careful cleaning. It is very easy to
damage a tongue.