||You don't need to memorize this diagram. But you do need to understand
how to find the notes. To do this, you'll need to know two things:
(1) the open tones of each string, and (2) the notes of the chromatic scale.
(1). The open tones (the note that sounds when the string is unfretted)
of the four strings are G, C, E, and A. This is the familiar "My
Dog Has Fleas" melody that all ukulele players know.
(2). Each time you move one fret higher on a string, you move one note
higher on the chromatic scale. The twelve notes of the chromatic
scale are A, A#/Bb, B, C, C#/Db, D, D#/Eb, E, F, F#/Gb, G, G#/Ab.
Looking at the diagram, you can see how the chromatic scale extends
up the fretboard, one note at a time, starting at the open tone for each
If you're wondering why the chromatic scale doesn't always have
a flat or sharp between each of the "natural" notes of the scale, take
a look at the scale as it shows up on a piano keyboard. The white
keys are the natural notes (A, B, C, ...) and the black keys are the sharps
and flats. The irregular pattern of sharps and flats is represented
in the irregular pattern of black keys on the piano. You can see
that there are no sharps or flats between B and C, or between E and F.