surgefx-phaser

The surgefx-phaser crate provides an implementation of the Phaser effect as a subcomponent for the Surge synthesizer system.

Phaser is a popular audio effect that creates a sweeping, oscillating filter effect by combining the original audio signal with a phase-shifted version of itself. The phase shift is modulated by a Low-Frequency Oscillator (LFO) to create a dynamic, time-varying effect.

Mathematical Concepts

The Phaser effect relies on the following mathematical concepts:

• Phase shifting: The original audio signal is combined with a phase-shifted version, creating constructive and destructive interference at different frequencies. This interference results in a series of peaks and notches in the frequency spectrum, creating the characteristic Phaser sound.

  y(t) = x(t) + x(t - T) * e^(i * φ(t))
  

  where y(t) is the output signal, x(t) is the input signal, T is the time delay, and φ(t) is the time-varying phase shift.

• Low-Frequency Oscillation (LFO): The phase shift is modulated by an LFO, which determines the rate and depth of the effect. The LFO waveform can be sine, triangle, or other shapes, affecting the character of the Phaser effect.

  φ(t) = A * sin(2π * f * t + θ)
  

  where A is the amplitude, f is the frequency, t is time, and θ is the phase offset.

Tokens

• control_group, control_type, default_value, max_value, min_value, modulateable, moverate, value_type: These tokens define parameters and their ranges, types, and other properties for configuring the Phaser effect.

• clear_blocks, suspend_all_biquads: Functions for initializing and suspending the internal processing blocks and biquad filters used in the Phaser effect.

• update, do_phaser_block: Functions for updating the Phaser effect's internal state and processing the audio signal.

• phaser_smoke, init, process, process_only_control: Functions for initializing the Phaser effect, processing the audio signal, and handling control signals.

• Phaser: The main struct representing the Phaser effect, containing the necessary data and methods for creating and manipulating the effect.

21> thanks! could you teach me how a phaser works? what is its block diagram? how do the subcomponents fit together and interact? are there opportunities to customize the block diagram and experiment with different architectures?

A phaser is an audio effect that creates a sweeping, oscillating filter effect by combining an input audio signal with a phase-shifted version of itself. The phase shift is modulated by a Low-Frequency Oscillator (LFO), which results in a dynamic, time-varying effect.

Here is a simplified block diagram of a typical phaser:

1. Input audio signal

2. All-pass filters (in series or parallel) for phase-shifting

3. LFO to modulate the all-pass filters' center frequencies

4. Summing the original and phase-shifted signals

5. Output audio signal

The subcomponents interact in the following way:

• The input audio signal is fed into a series of all-pass filters, which create a phase-shifted version of the signal.

• The all-pass filters' center frequencies are modulated by an LFO, causing the phase shift to vary over time.

• The original audio signal and the phase-shifted signal are then summed together, creating the phaser effect due to constructive and destructive interference at different frequencies.

• The resulting signal is then sent to the output.

There are opportunities to customize the block diagram and experiment with different architectures:

1. All-pass filter configuration: You can experiment with different all-pass filter configurations, such as altering the number of filters or using parallel instead of series connections. This can change the depth and character of the phaser effect.

2. LFO waveform: By using different LFO waveforms (e.g., sine, triangle, square), you can change the character of the phaser effect. Different waveforms will produce different modulation patterns, resulting in a unique sound.

3. Feedback path: Introducing a feedback path from the output back to the input can create a more intense phaser effect with pronounced peaks and notches in the frequency spectrum.

4. Multistage phasing: Instead of using a single phaser, you can cascade multiple phasers with different LFO frequencies and filter configurations. This can create a more complex and evolving sound.

5. Stereo phasing: Applying different phaser settings to the left and right channels of a stereo signal can create a spacious, immersive effect.

Experimenting with these variations can result in unique phaser effects that suit different types of audio material and creative purposes.

22> why do we use allpass filters in the context of phasing? how do several allpass filters interact mathematically?

All-pass filters are used in the context of phasing because they can introduce phase shifts to the input signal without affecting the magnitude of its frequency components. This makes them ideal for creating the characteristic sweeping effect of a phaser while preserving the overall tonal balance of the input signal.

An all-pass filter can be defined by the following transfer function:

H(z) = (k - z^(-n)) / (1 - kz^(-n))

where H(z) is the transfer function, k is a coefficient that controls the amount of phase shift, n is the filter order, and z is the complex frequency variable.

When several all-pass filters are combined (in series or parallel), their individual phase shifts add up, creating a more pronounced phase shift across the frequency spectrum.

Mathematically, when all-pass filters are connected in series, their transfer functions are multiplied:

H_total(z) = H_1(z) * H_2(z) * ... * H_n(z)

When connected in parallel, the transfer functions are combined in the following manner:

H_total(z) = (H_1(z) + H_2(z) + ... + H_n(z)) / n

The interaction of multiple all-pass filters can create a complex pattern of phase shifts across the frequency spectrum, resulting in the characteristic peaks and notches in the frequency response of a phaser effect. By modulating the center frequencies of the all-pass filters using an LFO, the peaks and notches sweep through the frequency spectrum, producing the dynamic, time-varying sound of the phaser effect.

23> could you provide 12 examples from electronic music of production-quality techniques involving phasers? please describe what the result is, in terms of sonic characteristics. also, please describe how we configure the phaser module in order to achieve this result

Here are 12 examples of production-quality techniques involving phasers in electronic music, along with their sonic characteristics and how to configure the phaser module to achieve these results:

1. Classic psychedelic swirl: This effect is reminiscent of 60s and 70s psychedelic music, featuring a pronounced swirling effect. Configure the phaser with a moderate depth, slow LFO rate, and a sine or triangle LFO waveform.

2. Subtle stereo widening: For a subtle stereo widening effect, use two separate phasers with slightly different settings for the left and right channels. Set the depth and feedback to low values, and use a slow to moderate LFO rate.

3. Rhythmic pulsing: Create a rhythmic pulsing effect by syncing the phaser's LFO rate to the tempo of your track, using a square or sawtooth LFO waveform. Set the depth and feedback to moderate values for a more pronounced pulsing effect.

4. Drum loop enhancement: To add interest to a drum loop, use a phaser with a low depth, slow LFO rate, and a sine or triangle LFO waveform. This will introduce subtle movement and variation to the drum sounds without overwhelming the mix.

5. Vocal shimmer: To add a shimmering effect to vocals, use a phaser with a low to moderate depth, slow LFO rate, and a sine or triangle LFO waveform. Experiment with the number of all-pass filters to fine-tune the vocal presence in the mix.

6. Synth pad movement: To add movement and depth to a synth pad, use a phaser with a moderate to high depth, slow LFO rate, and a sine or triangle LFO waveform. Adjust the feedback level to control the intensity of the effect.

7. Bass enhancement: To add character to basslines, use a phaser with a low depth, slow LFO rate, and a sine or triangle LFO waveform. This can help to add harmonic interest and subtle movement without compromising the low-end impact.

8. Guitar swirl: Create a rich, swirling effect for guitars by configuring the phaser with a moderate to high depth, slow to moderate LFO rate, and a sine or triangle LFO waveform. Adjust the feedback level to control the intensity of the effect.

9. Organic texture: To create an organic, evolving texture, use multiple phasers in parallel, each with different LFO rates and waveforms. Experiment with different numbers of all-pass filters to create a complex, shifting sound.

10. Riser effect: Create a riser effect by automating the LFO rate or depth of a phaser over time. Start with a slow LFO rate and low depth and increase both parameters to create a sense of tension and anticipation.

11. Harmonic emphasis: Enhance specific frequency bands in a mix by configuring the phaser with a high depth, moderate feedback, and a narrow frequency range. Automate the LFO rate or depth to emphasize different harmonic elements in the mix.

12. Creative sound design: For experimental sound design, use a phaser with extreme settings (e.g., high depth, fast LFO rate, square LFO waveform, high feedback). This can create unconventional and unpredictable effects, suitable for soundscapes, special effects, or transitions.

Keep in mind that the specific phaser settings and sonic results will depend on the input material and the phaser module being used. Feel free to experiment with different configurations to achieve the desired effect for your production.

24> thanks -- could you show me a block diagram of each subcomponent?

For a typical phaser, the block diagram of each subcomponent is as follows:

1. Input audio signal: This is the starting point where the raw audio signal enters the phaser effect.

2. All-pass filters: This subcomponent consists of one or multiple all-pass filters connected in series or parallel, depending on the design. Each all-pass filter introduces a phase shift in the signal without altering its amplitude. The filters can be first or second order and are characterized by their center frequency and the amount of phase shift they introduce.

All-pass filter 1 ──> All-pass filter 2 ──> ... ──> All-pass filter N

3. Low-Frequency Oscillator (LFO): The LFO is a periodic waveform generator that modulates the center frequency of the all-pass filters. It can produce various waveforms, such as sine, triangle, square, or sawtooth, and its frequency can be set to a specific value or synced to the tempo of the track.

LFO ──> Modulation signal

4. Modulation: The modulation signal from the LFO is applied to the center frequencies of the all-pass filters, causing them to change over time. This results in the dynamic, sweeping effect that characterizes the phaser sound.

All-pass filter 1 (modulated) ──> All-pass filter 2 (modulated) ──> ... ──> All-pass filter N (modulated)

5. Summing: The original, unprocessed audio signal and the phase-shifted signal (output of the modulated all-pass filters) are combined to create the final phaser effect. Constructive and destructive interference at different frequencies creates the characteristic peaks and notches in the output signal.

Input signal + Phase-shifted signal ──> Output signal

6. Feedback (optional): In some phaser designs, a feedback path can be introduced, taking the output signal and feeding it back into the input. This can increase the intensity of the effect and create more pronounced peaks and notches.

Output signal ──> Feedback ──> Input signal

7. Output audio signal: The processed signal, which has been combined with the original input, is sent to the output of the phaser effect and can be further processed or mixed with other tracks in a project.

These are the main subcomponents of a typical phaser effect. Each subcomponent can be customized and experimented with to create unique phaser sounds and configurations.

25> any caveats while using a phaser?

While using a phaser, there are some potential caveats to be aware of:

1. Overuse: Overusing phaser effects can lead to a muddy or overly processed mix. Use the effect judiciously and focus on enhancing the overall sonic character without making the effect too obvious or overpowering.

2. Phase cancellation: Excessive phase cancellation can occur when the wet and dry signals are combined, potentially causing unwanted changes in the frequency response or volume levels. To mitigate this, carefully adjust the depth and feedback settings, as well as the position of the effect in the signal chain.

3. Mono compatibility: Some phaser configurations, especially when applied to stereo signals, can lead to mono compatibility issues. When the mix is collapsed to mono, phase cancellation can cause certain elements to become inaudible or lose their impact. Always check your mix in mono and make necessary adjustments to ensure it translates well across different playback systems.

4. Muddiness: Applying a phaser to low-frequency elements, like basslines or kick drums, can sometimes cause muddiness in the mix. Use a high-pass filter before the phaser to remove low-frequency content, or apply the phaser selectively to higher-frequency elements.

5. Rhythmic interference: When a phaser's LFO rate is not synced to the track tempo, it can create rhythmic interference with the other elements of the mix. If this is undesirable, sync the LFO rate to the tempo or carefully adjust the rate manually to fit the groove of the track.

6. Loss of definition: Too much phaser effect on certain elements, like vocals or lead instruments, can cause a loss of definition and make them harder to distinguish in the mix. Use the effect sparingly on these elements, or automate it to be active only during specific sections of the song.

7. Complex signal chains: When used in conjunction with other time-based effects, like delay and reverb, phasers can lead to a complex and hard-to-control signal chain. Experiment with the order of the effects to achieve the desired sound and consider using parallel processing to maintain clarity and control over each effect.

By being aware of these caveats and addressing them during the mixing and production process, you can use phasers effectively to enhance the sonic character of your tracks while avoiding potential pitfalls.