A device and method for automatic tuning of a string Instrument, in particular, a guitar, comprising a recording device, for recording a tone generated by striking a string and for the output of a digital signal corresponding to the recorded tone, a memory device for storage of given digital signals which correspond to a desired tone, a comparator device for comparison of the digital signal output by the recording device with a digital signal corresponding to the desired tone stored in the memory device, an adjuster device for altering the tension of the strings, at least one actuator, for operating the adjuster device, a controller connected to the comparator device, which controls the at least one actuator using a bus line, by means of a difference determined in the comparator device between the signals representing the generated tone and the desired tone. The above is improved with relation to conventional techniques in so far as the above may be integrated in an instrument, in particular, a guitar, with minimal effect on the sound properties and with the smallest and least possible number of elements. The controller and the at least one actuator are arranged in the string instrument, on opposing sides of the strings viewed in the longitudinal direction of the strings and a string, made from a conducting material or wound or coated with such, is used as bus line between the controller and the at least one actuator. Furthermore, a method for the automatic tuning of a string instrument is disclosed.