Yes. A spring reacts to force by storing energy in the strain (aka stretching) it experiences. A crystal oscillator has the additional property that when it st

Yes. A spring reacts to force by storing energy in the strain (aka stretching) it experiences. A crystal oscillator has the additional property that when it stretches, it develops an electric field across it--and conversely, when an electric field is applied across it, it stretches. So you can make the crystal vibrate by putting a voltage across it, and this vibration is visible when you monitor the voltage. It's like striking a bell...the bell's vibration creates an audio vibration.