Final answer:
The keyboard sends a control signal to an oscillator to determine the pitch, analogous to how strings on a piano resonate to match the pitch of a sung note.
Step-by-step explanation:
The keyboard sends out a control signal to the oscillator which controls the pitch. In terms of physics, this can be related to the concept of resonance and periodic driving forces acting on a simple harmonic oscillator. When discussing a musical instrument like a piano, the comparison can be drawn that when a note is sung towards it with the dampers raised, the corresponding strings resonate and produce the same note due to them vibrating at their natural frequency. In electronic instruments, the keyboard uses control signals to direct the oscillator to produce a certain frequency, which in turn dictates the pitch of the note played.