Two performers were necessary to play this organ, just as nowadays we play four-hand music on the piano.  The keys went down with such difficulty that the players had to use their elbows or fists on each key; therefore it is easy to see that, at the most, only four keys could be pressed down at the same time.  On the other hand, each key when pressed down or pushed back (for in the early organs the keyboard was perpendicular) gave the wind from the bellows access to ten pipes each, which were probably tuned in octaves or, possibly, according to the organum of Hucbald, in fifths or fourths.  This particular organ had two sets of keys (called manuals), one for each player; there were twenty keys to each manual, and every key caused ten pipes to sound.  The compass of this organ was restricted to ten notes, repeated at the distance of an octave, and, there being four hundred pipes, forty pipes were available for each note.  On each key was inscribed the name of the note.  As may be imagined, the tone of this instrument was such that it could be heard at a great distance.

There were many smaller organs, as, for instance, the one in the monastery of Ramsey, which had copper pipes.  Pictures of others from the twelfth century show that even where there were only ten pipes, the organ had two manuals, needed two players, and at least four men for the bellows.  The great exertion required to play these instruments led to the invention of what is called “mixtures.”  From the moment fifths and fourths were considered to sound better together than the simple notes, the pipes were so arranged that the player did not need to press two of the ponderous organ keys for this combination of sounds.  One key was made to open the valves of the two sets of pipes, so that each key, instead of sounding one note, would, at will, sound the open fifth, fourth, or octave.  With the addition of the third, thus constituting a perfect major triad, this barbarous habit has come down to our present day almost unchanged, for by using what is called the “mixture stop” of our modern organs, each key of the manual gives not only the original note, but also its perfect major triad, several octaves higher.

Originally the organ was used only to give the right intonation for the chanting of the priests.  From the twelfth century, small portable organs of limited compass were much used; although the tone of these instruments was necessarily slight, and, owing to the shortness of the pipes, high in pitch, the principle of the mechanism was similar to that of the larger instruments.  They were hung by means of a strap passed over the shoulders; one hand pressed the keys in front of the pipes (which were arranged perpendicularly), and the other hand operated the small bellows behind the pipes.  These small instruments rarely had more than eight pipes, consequently they possessed only the compass of an octave.  With slight variations, they were quite universally used up to the seventeenth century.  Organ pedals were invented in Germany about 1325.  Bernhard, organist of St. Mark’s, Venice (1445-1459), has been credited with the invention of organ pedals, but it is probable that he merely introduced them into Italy.