What is an octave?

In music, an octave is a sound interval, grouping all notes whose frequencies are between a frequency reference f and the double 2xf.
For instance: C 220 is a note whose frequency is 220Hz, so we can define one octave including many sounds, all these sounds have a frequency higher than 220Hz and lower than 440Hz. For every octave, we can define 8 different notes: A B C D E F G A
Moreover, we can add sharps and flats: A# C# D# F# G#

To know which octave we are talking about, we give a number indicating the octave.
In the array below, an octave is an entire column plus the first note of next column.

Note\Octave 1 2 3 4 5 6 7 8
C32.70 Hz65.41 Hz130.81 Hz261.63 Hz523.25 Hz1 046.50 Hz2 093.00 Hz4 186.01 Hz
C#34.65 Hz69.30 Hz138.59 Hz277.18 Hz554.37 Hz1 108.73 Hz2 217.46 Hz4 434.92 Hz
D36.71 Hz73.42 Hz146.83 Hz293.66 Hz587.33 Hz1 174.66 Hz2 349.32 Hz4 698.64 Hz
D#38.89 Hz77.78 Hz155.56 Hz311.13 Hz622.25 Hz1 244.51 Hz2 489.02 Hz4 978.03 Hz
E41.20 Hz82.41 Hz164.81 Hz329.63 Hz659.26 Hz1 318.51 Hz2 637.02 Hz5 274.04 Hz
F43.65 Hz87.31 Hz174.61 Hz349.23 Hz698.46 Hz1 396.91 Hz2 793.83 Hz5 587.65 Hz
F#46.25 Hz92.50 Hz185.00 Hz369.99 Hz739.99 Hz1 479.98 Hz2 959.96 Hz5 919.91 Hz
G49.00 Hz98.00 Hz196.00 Hz392.00 Hz783.99 Hz1 567.98 Hz3 135.96 Hz6 271.93 Hz
G#51.91 Hz103.83 Hz207.65 Hz415.30 Hz830.61 Hz1 661.22 Hz3 322.44 Hz6 644.88 Hz
A55.00 Hz110.00 Hz220.00 Hz440.00 Hz880.00 Hz1 760.00 Hz3 520.00 Hz7 040.00 Hz
A#58.27 Hz116.54 Hz233.08 Hz466.16 Hz932.33 Hz1 864.66 Hz3 729.31 Hz7 458.62 Hz
B61.74 Hz123.47 Hz246.94 Hz493.88 Hz987.77 Hz1 975.53 Hz3 951.07 Hz7 902.13 Hz

Obviously, the more an Ocarina can play notes of this array; the bigger the number of songs it can handle. So before buying an ocarina, check the instrument's capacity to play the notes you want to play.

Here is the video of classical music played with a triple ocarina: