Wavetable synthesis is a technique that produces natural sounds. When the sound comes from an actual musical instrument, the process separates a single note into a sequence of wavetables.
Analog Oscillators
Analog oscillators offered four basic oscillator waveforms until a new form of audio synthesis appeared. Around 1970, Waldorf Music Company launched the PPG wave synthesizer, a digital oscillator known as wavetable oscillator. This wavetable oscillator revolutionized the audio synthesis universe because it was able to carry up to sixty-four wavetables.
But What Is a Waveform?
The waveform involves samples that operates for a single period of the general wave shape. There is a mechanism that works by changing the wave shape as the musical notes progress. Hence, producing a quasi-periodic function within a specific time. This process can use envelopes, velocity, or LFOs to step through the waveforms.
Wavetable Synthesis: How It Works
People recognize the wavetable synthesis technique for its memory saving capacities. It uses looping, pitch shifting, re-sampling, and aliasing noise to achieve it.
The first of this memory saving capacities is looping. It is one of the most common ones. In this case, the need for memory decreases as sampled sound segments loop. Let’s remember that a sound involves two main sections: attack and sustain. Firstly, attack refers to as the initial part of the sound, where you can quickly alter both the amplitude and the spectral characteristics. Secondly, sustain refers to the area where sounds change more slowly. Wavetable synthesis saves a lot of memory by only storing a short segment of the sustained area of the waveform and looping this segment back during playback.
In second place comes pitch shifting. It happens when you store only a few notes. The user can shift the pitch to the nearest note in order to achieve the desired pitch. When the pitch is far away, the tone will sound quite unnatural.
Thirdly, re-sampling occurs when the recording of a low note on an acoustic bass does not have many high-frequency partials. When this happens, the user is able to re-sample the wavetable for that particular note to a lower sample rate. If used, the timbre will not be affected.
Lastly, you achieve aliasing noise by shifting the pitch of a stored sound sample. This can also limit the amount of pitch shifting. Sounds with high harmonic content have more problems with aliasing noise, whereas low-pass filtering and oversampling can quickly remove unwanted noises.
Wavetable Synthesis: Conclusions
This type of synthesis is one of the most popular ones. If you want to go on learning about other types, we recommend you check the subtractive and the granular out.
