Sound Morphing has been one of my deep interests since my work experience with Benti (a Swiss start-up, 2013). One of the first experiments I conducted involved using convolution with pulse responses to transform guitar sounds. I used different shapes and materials for pulse responses to simulate various and sometimes unusual guitar physics (such as plastic strings, extremely warm environmental conditions, and so on). The results were intriguing, and I continued exploring this domain in subsequent years.
Over time, I focused mainly on four topics or techniques:
1. Adaptive Waveshaping
This technique dynamically alters the shape of an audio waveform in real time. Unlike static waveshaping, where a fixed transfer function is applied, adaptive waveshaping adjusts the transfer function based on the characteristics of the input signal. The goal is to dynamically modify the timbre and harmonic content of the sound, creating effects ranging from subtle warmth and saturation to more aggressive distortion and dynamic range compression.
- Using the input signal's amplitude to control the amount of distortion.
- Using frequency information to shape different parts of the spectrum differently.
- Using envelope followers to create dynamic changes in the waveshaping over time.
2. Guitar Warmer
This technique focuses specifically on enhancing the spectral content of guitar recordings, bringing out harmonics and tonal nuances. The goal is to add warmth, richness, and clarity to the guitar sound, making it more vibrant and present. My exploration involved:
- Spectral analysis to identify frequencies that could be enhanced.
- Boosting specific frequency bands or harmonics.
- Dynamic processing to avoid over-emphasizing certain frequencies or creating unwanted artifacts.
- Time-domain processing to add subtle warmth and saturation.
Examples of sounds achieved with these techniques are available at this link.
3. Spectral Shaper
This technique manipulates the frequency spectrum of a sound using various methods. The goal is to sculpt the tonal balance of the sound, emphasize or attenuate specific frequencies, and create unique sonic textures. Key areas I explored include:
- Frequency domain processing.
- All-pass filters for local spectral approximation and frequency wrapping.
Here's a paper I presented while working at Benti: View Paper.
4. Morphing, Particularly with the Voice
This technique involves smoothly transitioning between two or more sounds or timbres. The goal is to create seamless and dynamic changes in the sound, often resulting in unique and evolving textures. One specific area of interest was voice-controlled morphing, where the voice acts as a control signal to modulate various parameters of the sound, creating a more organic and expressive form of morphing.