Strings (tennis)
The material used in tennis string can significantly affect a player's performance, and even health. Several materials are used to make tennis strings. They vary in terms of elasticity, durability, rebound efficiency, tension holding capability, and manufacturing cost, among other considerations.
Michael Masley
The lid can be flexed, which will bend the pitch. While many stringed instruments can pitch bend, others bend along only one direction, altering the pitch of only a single set of strings, and by changing the tension of all strings together, their musical interval relationships stay constant. By having two courses of strings which are not parallel, the pitch bending changes the tonal relationships between the two sets of strings. If the instrument is flexed parallel to one set of strings, that set of strings remains unaltered, but the perpendicular set of strings deepens in pitch. If the instrument is flexed at an angle to both sets of strings, the pitch of both sets varies in a mathematically related fashion. Past a certain degree of flex, the two courses of strings touch and dampen each other, and the sounds produced by the spring dominate.