Piano tuning is the adjustment of the tension of each string in the piano to set its optimal pitch.  Increasing a strings tension causes its pitch to rise and lowering its tension causes the pitch to drop.  
Although (most) pianos have 88 keys, they usually have over 200 strings.  Most notes actually have three strings, while the lowest notes have either two or one string per note.

Piano tuning 

Gary's Piano Service

Piano Tuning and Repair

Gary's Piano Service is a graduate of the famous "Yamaha Little Red School House " and Steinway Concert Technician School. Gary's Piano Service has the education and expertise to tune , regulate, repair, and voice your piano no matter what make or style.  ​ You have heard the sounds of few of our clients like Roger William, Barry Manilow, Harry Connick Jr; Lionel Ritchie and John Legend! A few locations include are College of the Desert, The Annenberg Theater in Palm Springs, Riverside Community College, and Fantasy Springs Casino in the Coachella Valley, also Schools , Churches and Music Teachers year after Year!