Because of the problem of inharmonicity, electronic piano tuning devices used by piano technicians are not designed to tune according to a simple harmonic series. Rather, the devices use various means to duplicate the stretched octaves and other adjustments a technician makes by ear. The most sophisticated devices allow a technician to make custom inharmonicity measurements—simultaneously considering all partials for pitch and volume to determine the most appropriate stretch to employ for a given instrument. Some include an option to simply record a tuning that a technician has completed by ear; the technician can then duplicate that tuning on the same piano (or others of similar make and model) more easily and quickly.