New Approaches to Digital subtractive synthesis

Computationally efficient oscillator and filtering algorithms for digital subtractive synthesis are discussed. The oscillators algorithms include the recently proposed differentiated parabolic waveform generator and its modification. The algorithm generates a signal that sounds similar to the analog sawtooth waveform, because it suppressed aliasing that occurs due to sampling of a non-bandlimited waveform. A modified version of the nonlinear digital Moog ladder filter is introduced. The new structure reduces the computational cost of the nonlinear digital Moog filter by using a single nonlinearity in the feedback loop instead of four nonlinear functions inside filter sections. The new digital Moog filter structure also decouples the cutoff and the resonance parameters and offers several response types by selecting a weighted sum of different output points. Figure 1. A typical block diagram of subtractive synthesis as it was implemented in the Prophet 5 synthesizer in late 1970s. In this paper, we discuss new versions of oscillator and resonant filtering algorithms that can sound like old analog synthesizers. 2. SUBTRACTIVE SYNTHESIS The electronic music modules introduced by Robert A. Moog in mid-1960s [6] are one of the most important innovations in music technology. A few years later, his company introduced products where the various modules, such as oscillators, filters, and amplifiers, were integrated into a single portable unit. Subtractive synthesis was the main principle used in these instruments. Minimoog was one of the most popular analog synthesizers in 1970s.