fig1 is a perspective view of the invention &# 39 ; s preferred embodiment exterior rectangular housing 1 . this particular housing has the same height ( h ) and length ( l ) dimensions with a ( w ) dimension slightly more than half that of the height . visible on the near housing &# 39 ; s side 2 are the recessed timing belt 3 and its connected upper 5 and lower 7 pulleys . as shown is the space adjustment thumb wheel 9 used to adjust internal tuning wrenches which engage the piano &# 39 ; s tuning pins . fig2 is a perspective exploded view showing the mentioned components and the internal components used in fig1 . an electrically operated gear motor 11 is connected by its engaging shaft 13 to the center hole 15 in upper timing pulley 5 . motor mounted bolt ends 17 extend through recessed holes in housing side 2 where nut and washers 19 fix them and their motor to the housing . the lower driven timing pulley 7 has a center hub which is set screwed to an hexagonal spline shaft 21 which engages with and extends to the end of rotatable drive shaft 23 . mounted on the drive shaft is a worm gear assembly 25 . beside the worm gear assembly an actuator link slide 27 is used to transmit linear motion from the push / pull solenoid 29 to the drive shaft to move the drive shaft left , right or center . the worm assembly 25 rides in a cylindrical grooved guide way 31 formed in the lower housing section 33 which section receives the actuator link 27 in a right angled housing cutout 35 . several machine screws 37 extend through holes in side 2 to mount lower section 33 to it . a gear box cover plate 39 with its own screws 41 is fastened to the top of housing section 33 at its two facing upper adjacent ledge edges 43 . also , mounted in housing section 33 next to worm assembly 25 and covered by plate 39 are the three spaced identical worm gears 45 . a lead screw pin 47 used to adjust the piano tuning pin spacing engages the worm gears 45 as best shown in fig3 . three aligned nylatron bearing blocks 49 mount the lead screw and the worm gears 45 . the center block is stationary and is part of housing 33 . at the center of the lead screw pin 47 is a smooth spool section 51 which sets into the stationary center block 49 and has two threaded surfaces 53 on either side ( see fig2 ). the lead screw pin 47 does not touch the worm gears and is threaded into the bearing blocks 49 while the worm gears 45 rotate in the blocks and only engage the worm 25 . by shifting drive shaft 23 either to the left , right or center by solenoid 29 one can drive each of the worm gears 45 either direction independently . extending from and connected to each worm gear is a tuning wrench head 55 used to connect to the piano &# 39 ; s tuning pins . thus , each piano note can have its three strings tuned in unison by these wrenches 55 . fig4 is an electronic circuit diagram for the components . as shown , the basic circuit has a tuning unit with an interconnected condenser microphone 57 , a digital readout 59 and led ( light emitting diode ) indicators 61 . sounds from the piano &# 39 ; s strings are picked up by the microphone , amplified and compared electronically as detailed below . electric power to run the unit comes from a conventional ac 120 volt line . the microcontroller outputs a signal to both the motor and solenoid drives . these two drives control the movement of the gear motor 11 and solenoid 29 , respectively . all these components are conventional electronic components connected as shown to perform as described . fig5 is a cross sectional view detailing the drive train used to move the worm assembly 25 in detail . the hexagonal spline 21 is mounted within the center of drive shaft 23 . overrunning clutches 65 surround both the drive shaft and spline . brass washers 67 retain a compression spring 69 which rides in the same bore as the spline and bears against it . a retaining ring 71 maintains the washers and spring in place . at the unit &# 39 ; s pulley 7 engaging end a protruding hub 73 fits into the end housing 2 . fig6 is a cross sectional side view of a gear components joining to the drive shaft and associated components . in this view , the worm gear 45 joins the drive shaft 25 and its associated components . the shaft of the push / pull solenoid 29 is mounted to the actuator link slide 27 . movement of the link end 75 ( see fig2 ) will result in the reciprocal movement of the drive shaft 25 . this movement causes associated clutches to become engaged or disengaged with the drive shaft . the lead screw 47 ( see fig3 ) is connected to the outside housing thumb wheel 9 such that rotation of the thumb wheel will cause the screw to rotate and adjust the worm gear bearing blocks and thus the carried worm gears 45 . as screw 47 rotates it can either spread or squeeze ( depending on the direction of rotation ) the associated worm gears 45 together since these gears are mounted in the movable bearing blocks 49 and therefore they also move with the rotation of threaded screw member 47 . the spacer spool 51 ( see fig2 ) is fixed linear to the rotatable screw 47 and its spacing with respect to the two adjacent screw threaded bearing blocks varies based on the carried screw &# 39 ; s direction of rotation . fig7 ( a ) shows a cross sectional view of the engagement between the worm gears and the wrench heads . a twelve degree freedom of movement exists to facilitate insertion of the piano &# 39 ; s tuning pins into the wrench heads . this is needed as the piano pins may be randomly positioned in orientation . the interior pin engaging surface of the wrench heads is shown in cross section in fig7 ( b ). each of the three wrench heads has a 16 point drive to engage one square piano tuning pin . fig8 is a perspective view of the wrench heads 55 engaging the piano &# 39 ; s tuning pins 77 of a typical piano 79 . to tune a piano note it should be recognized that all musical sounds are a mixture of pure sinusoidal tones at different frequencies and amplitudes . there is a fundamental tone which is the basic musical note that we hear . this fundamental tone has a larger amplitude than its associated harmonic tones and , for the piano , the lowest frequency of all its tones . the rest of the tones are harmonic overtones and their frequencies and amplitudes determine the &# 34 ; timbre &# 34 ; or distinctive sound of the instrument . a spectral map of these tones is like a signature for an instrument . a piano is strung in groups of one , two or three strings that are tuned to the same note and are struck simultaneously when playing . when a piano is out of tune these strings will be at slightly different frequencies but they will still have the same spectral signature . with the present invention , a piano is tuned note by note , sequentially starting with its top or highest frequency note . the wrench heads 55 are placed on the proper tuning pins 77 and the corresponding key is struck manually . the sound is picked up by the piano tuner &# 39 ; s microphone 57 and amplified . exact values for the correct frequency of all 88 notes have been digitally stored in memory . first , a tunable band - pass filter , like a radio dial , is tracked from low frequency upward until the fundamental tone is located . the appropriate frequency is then determined from the filter &# 39 ; s tuning value and the closest corresponding note stored in memory is displayed . the operator verifies that this is the correct note by pressing the tune button . the filter is then tuned to a frequency below the fundamental tone . the microprocessor then controls the motor and the clutch automatically for one tuning pin to pull it &# 39 ; s frequency down until it is seen to appear and disappear from the frequency window . this process is repeated for the note &# 39 ; s other two strings . then the band - pass filter is tuned just below the correct frequency as stored in memory and the strings 81 are tuned upward , one at a time , until each is seen to appear and then disappear from the frequency window . all the strings are now in tune and the process is repeated for the next note down , etc . although the automatic piano tuner and the method of using the same according to the present invention has been described in the foregoing specification with considerable details , it is to be understood that modifications may be made to the invention which do not exceed the scope of the appended claims and that modified forms of the present invention done by others skilled in the art to which the invention pertains will be considered infringements of this invention when those modified forms fall within the claimed scope of this invention .