Abstract: In a magnetic recording disk file in which one or more magnetic sliders rest on the surfaces of the disks when the disks are not rotating, a short oscillatory micromotion is imparted to the slider or sliders prior to starting rotation of the disks, this micromotion serving to free the slider or sliders from any stiction forces tending to bind them to the disk surface.

Abstract: A stroboscopic tuning device for a stringed musical instrument that is mounted on the musical instrument adjacent to the strings to be tuned. A solid state circuit employs a frequency generator, such as a piezoelectric crystal oscillator or a tuning fork oscillator, to operate the stroboscopic light source at a preselected frequency. In the use of the device, a string is plucked, and when the vibratory motion of the plucked string is either the fundamental frequency or the harmonic frequency of the preselected operating frequency of the stroboscopic light source, the string will appear to an operator to be in a nonvibrating condition. At that time, the string is tuned or adjusted to the desired tone.