A system is disclosed for holding a musical instrument, such as a guitar, to a vertical post, such as a lamp post. An upper clamp is adapted for clamping to the vertical post and includes an instrument neck holder for engaging an upper portion of the musical instrument. A lower clamp is adapted for clamping to the vertical post and includes an instrument base holder for engaging a lower portion of the musical instrument. Each clamp preferably includes two arcuate jaws each terminating at one end at an actuator portion pivotally fixed to a pivot rod. A coil spring surrounds the pivot rod and biases the jaws towards each other, such that when the actuators are squeezed toward each other the jaws are forced to pivot away from each other against the urging of the coil spring. Each clamp may be adjusted vertically on the post so as to allow musical instruments of varying sizes to be used with the system. The instrument neck and base holders each conform to the shape of a part of the musical instrument and are preferably padded.