A triangular chisel shape stylus used to produce a master disc. The cutting stylus was inclined from the vertical by 15 degrees from 1964-197?, and 20 degrees since then according to the IEC standard. However. a +5 tolerance is permitted. Owing to the elasticity of the disc material, there is a springback effect after the cutter has passed. This reduces the tracking angle which together with the tolerance means that the angle can differ considerably from one record to another. The cutter traverses the dise tangentially, in a straight line from disc edge to centre. The cutter response is termed constant velocity, which means its velocity is the same for all frequencies. The amplitude therefore increases as the frequency drops, at the rate of 6 dB/octave. Large low-frequency stylus excursions are avoided by cutting the bass while treble is boosted to improve signal to noise ratio. These contours roll off either side of a short flat region centred on 1 kHz, to form the RIAA recording characteristic.