Recent Advances in Real-Time Musical Effects, Synthesis, and Virtual Analog Models

Real.-time musical effects processing and synthesis play a part in nearly all musical sounds encountered in the contemporary enviroflDlent. Virtually all recorded or electrically amplified music in the last few decades uses effects processing, such as artificial reverberation or dynamic compression, and synthetic instrument sounds play an increasingly larger part in the total musical spectrum. Furthermore, the vast majority of these effects are presently implemented using digital signal processing (DSP), mainly due to the flexibility and low cost of modern digital devices. For live music, realtime operation of these effec.:ts and synthesis algorithms is obviously of paramount importance. However, also recorded music typically requires real-time operation of these devices and algorithms, because performers usually wish to hear the final, processed sound of their instrument while playing. The purpose of this article is to provide the reader with an overview of some of the recent advances in this fascinating and commercially active topic. An exhaustive review of all novel real-time musical effects processing and synthesis would fiU a book. In fact, an earlier review on digital audio effe·cts can be found in the book [ I] and in a recent book [ 2], while reviews of virtual analog modeling and digital sound synthesis can be found in articles [3] and [4], respectively. A tutorial on virtual analog oscillator algorithms, which arc not tackled in this paper, has been written by Viilimaki and Huovilainen [5] . Also, musical synthesis and effects applications for mobile devices have been reported in [6]. In order to conveniently fit in a single journal article, a selection of some of the most active subtopics under this exciting research field have been chosen for presentation here. The organization of this review is as follows: adaptive effects processing algorithms, such as the adaptive FM technique, are reviewed in Section 2. Section 3 discusses the emulation of vintage delay and reverberation effects, while recent advances in tube amplifier emulation are studied in Section 4. Real-time simulation of an interesting analog effects device, the voltage-controlled filter, is reviewed in Section 5, and recent advances in sound synthesis and processing languages are discussed in Section 6. Finally, Section 7 concludes the review