Only peterson strobe tuners respond at the speed of light to display relative tuning of any audio source to 0.1 of a cent (1/1000 of a semitone) accuracy. In addition to the visual strobe indication, the Autostrobe 590 can function as an audio tuner by means of an Audio Out section which combines input sound with reference-pitch tones into headphones or an internal speaker. NEW! AUTOMATIC NOTE SELECTION NEW AUTOMATIC NOTE TRACKING - the audible tuner "tracks" the automatic note selection. NEW! AUTOMATIC IMAGE CLARITY AND CONTRAST CONTROL - internal compensation for optimal viewing over a wide range of source pitch and volume. NEW! IMPROVED CLARITY FOR UPPER AND LOWER REGISTER NOTES - +2/-1 display feature shifts the strobe patterns into more visible middle ranges bass note patterns can be displayed two octaves higher and treble note patterns can be displayed one octave lower in strobe display. NEW! EASY TRANSPOSITION - strobe patterns appear at the correct note for Bb, F, and Eb instruments. NEW BUILT IN METRONOME HEADPHONE JACK - for ear training and private tuning or practicing with electric instruments. BUILT IN AUDIBLE TUNER BUILT IN SPEAKER AND OUTPUT JACK ACCESSORIES - external mics, footswitches, and carry cases available.