Octave designations provide a method to correctly identfy every possible musical note from the lowest to highest pitches. The first system was created by Guido d'Arezzo in the 11th century called Gamut (from the lowest note in the scale "gamma ut"). This system was used through the 18th century. Hermann von Helmholtz (German acoustician) developed a system based on the notes of the organ. There are alternate ways to express the unique octaves, two of which are shown in the Appendix. This is probably the most recognized system in the field of music for many years.
In 1939, The Acoustical Society of America proposed another system that numbers the octaves from the lowest to the highest. This system is known as Scientific Pitch Notation (SPN), American Standard Pitch Notation (ASPN), International Pitch Notation (IPN).