Pianos are unusual compared to most other instruments in that the scale of the piano "stretches" as the pitch goes up. This occurs because stiff piano wire causes the harmonics for each note to "stretch" away from a simple mathematical relationship, i.e. the first harmonic is just a bit more then twice the fundamenatal frequency, the second harmonic is just a bit more again than 3 times the fundamental etc. This property is called inharmonicity and causes havoc if you try to tune the top note in a piano octave to twice the frequency of the bottom one. Because the harmonics stretch away so do the octaves on a piano, until at the top you get about half a semitone sharp compared to other instruments and at the bottom you get about a quarter of a semitone flat. The bend in the pitch of a well tuned piano follows a curve called a Railsback curve, or usually called a tuning curve. If you don't stretch a piano like this it sounds TERRIBLE.

The logo is a stylised tuning curve representing the ideal harmonic goal for a great sounding piano.