Virtual analog synthesis refers to the real-time simulation of
electronic music synthesis, which has been traditionally implemented
using analog electronics. Around 1995, music technology companies
started to develop digital musical instruments based on the virtual
analog approach. In some products, samples are used to play back old
sounds. We are developing discrete-time algorithms to simulate the
analog filters and the waveform generation of analog music
synthesizers. This work can be seen parallel to our physical modeling
research, where we design computational simulations of acoustic
systems - in virtual analog synthesis, computational simulations of
electronic systems are designed. A related topic is the simulation of
tube amplifiers used by electric guitar, bass, and electric organ
players. This problem is difficult due to nonlinearities in the tube
behavior. Our goal is to obtain physically valid digital models for
tube amplifiers. This implies accurate imitations of all electrical
parts of the amplifier. A further topic of interest is the modeling of
analog effects processing boxes, such as phasers and flangers.
The Minimoog was one of the most successful analog music synthesizers (Photo by Laurent de Soras).
The following table lists our virtual analog synthesis and audio effects - related research in inverse chronological order. For some publications, the PDF-file and a companion web-page containing sound
examples are provided. These can be found in the leftmost column.
|Publication ||Short description
V. Välimäki and A.
Huovilainen, "Antialiasing oscillators in subtractive synthesis," IEEE Signal Processing Magazine, vol. 24, no. 2, pp.
116–125, March 2007.
Signal processing techniques for implementing digital waveform oscillators with reduced aliasing are reviewed. Currently known
methods are classified, briefly reviewed, and compared. A new method based on polynomial bandlimited step functions (PolyBLEP) is
introduced. An auditory error measure, the noise-to-mask ratio (NMR), is used for evaluating the sound quality.
|| M. Karjalainen
and J. Pakarinen,
"Wave digital simulation of a vacuum-tube
IEEE International Conference on
Acoustics, Speech and Signal Processing
(ICASSP'06), Toulouse, France, May
discusses wave digital simulation of tube
amplifier stages, typical e.g. in guitar
amplifiers. A new real-time model is
introduced and different implementation
techniques are presented.|
V. Välimäki and A. Huovilainen, "Oscillator and Filter Algorithms for Virtual Analog Synthesis", in
Computer Music Journal, vol. 30, no. 2, 2006.
algorithms for the generation of
alias-free digital versions of classical
analog waveforms (the sawtooth, pulse, and
triangular wave) are
introduced. Modifications and
simplifications to the digital nonlinear
model of the Moog ladder filter proposed
previously by Huovilainen are
A. Huovilainen, "Enhanced digital models for analog modulation effects", in Proc. 8th Int. Conf. on Digital Audio Effects (DAFx'05), pp. 155-160, Madrid, Spain, Sept. 2005.
operation and non-idealities of analog
phaser and flanger / chorus effects are
discussed. Two new digital models for
phaser and one for flanger / chorus are
presented that more closely match the
operation of the analog
R. Trausmuth and A. Huovilainen, "Powerwave - A high performance single chip interpolating wavetable synthesizer", in Proc. 8th Int. Conf. on Digital Audio Effects (DAFx'05), pp. 293-296, Madrid, Spain, Sept. 2005.
a high quality wavetable synthesizer is
presented. The synthesizer is implemented
with a single Xilinx FPGA chip containing
both audio generation and control
A. Huovilainen and V. Välimäki, "New Approaches to Digital Subtractive Synthesis", in Proc. Int. Computer Music Conf. (ICMC'05), Barcelona, Spain, pp. 399-402, Sept. 2005.
presents new methods for digital
subtractive synthesis that have both low
computational cost and relatively high
quality. The DPW algorithm for producing
reduced alias sawtooth waveform is
reviewed. A new variant of the digital
Moog filter with multiple responses and
low cost non-linearity is also
V. Välimäki and A. Huovilainen, "Virtuaalista nostalgiaa - digitaalinen vähentävä äänisynteesi", Musiikki, vol. 35, no. 1-2, pp. 78-98, 2005.
|This is a review of oscillators and
resonant filters for digital subtractive
music synthesis in the Finnish
language. The DPW sawtooth algorithm, the
simplified nonlinear Moog filter, and two
examples of digital synthesizer patches
are briefly explained. |
V. Välimäki, "Discrete-Time Synthesis of the Sawtooth Waveform with Reduced Aliasing", IEEE Signal Processing Letters, vol. 12, no. 3, pp. 214-217, March 2005.
introduces a new efficient signal
processing technique, called the DPW, to
generate an alias-free sawtooth waveform
for virtual analog synthesis. The
algorithm differentiates a piecewise
parabolic waveform, and it is easy to
implement with a computer. Two variants of
the algorithm are given, one of which
employes multirate signal
N/A || M. Karjalainen,
T. Mäki-Patola, A. Kanerva, A. Huovilainen,
and P. Jänis, ''Virtual Air Guitar,'' in
Proceedings of AES 117th
Convention, preprint no. 6203, San
Francisco, CA, USA, October 28-31,
|Signal processing and gesture-control
methods are discussed that enable playing
of an electric guitar synthesizer by
waving your hands in the air. Highly
entertaining real-time demonstrations have
been implemented using these
techniques. For more info, see
A. Huovilainen, "Non-linear Digital Implementation of the Moog Ladder Filter", in Proc. 7th Int. Conf. Digital Audio Effects (DAFx'04), pp. 61-64, Naples, Italy, October 5-8, 2004.
analyzes the structure and behaviour of
the Moog ladder filter. A large-signal
model is presented and discretized to
yield a digital model that correctly
simulates the non-linear behaviour. An
alternative method of tuning correction is
also presented. |