This demonstration will use optical, magnetic, and piezoelectric guitar pickups to measure time signals and frequency spectra for the displacement, velocity, and force (measured at the bridge) of a plucked and struck guitar string. For the plucked string, experimental observations of the displacement and velocity of a point on the string agree very well with theory. Frequency spectra also agree well with theoretical predictions and highlight the differences in timbre between the audio signals obtained with each pickup. The demonstration will briefly discuss theoretical time signals and frequency spectra for a point on a plucked string, show measured time signals and frequency spectra from the various pickups, and compare audible examples of the sounds from the pickups for a plucked string. For the struck string, a simple theory approximates the basic shape of the string displacement and velocity, but dispersion effects in the string and the reality of the hammer-string interaction are evident in the measured string response. If time permits, a demonstration of the sound and spectrum of a compound string will be included.