Yamaha OPL

Sound chip series by Yamaha The OPL (FM Operator Type-L) series is a family of sound chips developed by Yamaha. It consists of low-cost sound chips providing FM synthesis for use in computing, music and video game applications. The OPL series of chips enabled the creation of affordable sound cards for IBM PC compatibles in the late 1980s such as the AdLib and Sound Blaster, effectively becoming a de-facto standard until they were supplanted by "wavetable synthesis" cards in the early-to-mid 1990s. Internal operation The internal operation of the chips is completely digital. Each FM-tone is generated by a digital oscillator using a form of direct digital synthesis. A low-frequency oscillator and an envelope generator drive an FM operator to produce floating-point output for the DAC. Decapsulation of the chips shows two look-up tables, one for calculating exponents and one for log-sine. This allows the FM operator to calculate its output without any multipliers, using the formula exp ⁡ [ log ⁡ sin ⁡ [ φ 2 + exp ⁡ [ log ⁡ sin ⁡ [ φ 1 ] + A 1 ] ] + A 2 ] {\displaystyle \exp[\log \sin[\varphi _{2}+\exp[\log \sin[\varphi _{1}]+A_{1}]]+A_{2}]} and two 256-entry look-up table