MUSICAL TONE GENERATING METHOD

摘要

PROBLEM TO BE SOLVED: To lighten the process load of musical tone waveform generating operation on a CPU by approximating the envelope characteristics of a waveform with a polygonal line and calculating an envelope value at each sampling timing point. SOLUTION: In this process, an envelope is approximated with a polygonal line with length corresponding to a one-frame time to find an envelope value at each sampling timing point. Namely (1) an initial value is denoted as I and the envelope value I.S' (or I.R') of a 128th sample is calculated by using the attenuation rate S' or R' in EG control information. (2) The difference between I.S' (or I.R') and I is divided by 128 to calculate an increment or decrement Δin each sampling cycle. (3) The increment or decrement Δis repeatedly added to the initial value I in each sampling cycle to find the envelope value in sampling timing.