SynapSeq v4.42.0

[ruanklein]

SynapSeq v4.42.0 expands the sound-design language with user-defined waveforms and transition curves, new stereo and frequency-domain controls, broader Doppler support, and faster audio rendering.

This release gives sequence authors more control over both the shape of generated sound and the way parameters evolve over time, while reducing the time required to export WAV and MP3 files.

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Highlights

Custom Waveforms

SynapSeq sequences can now define reusable periodic waveforms directly in SPSQ with the new @waveform option.

@waveform softpulse 0 0 20 60 100 60 20 0

focus
  waveform softpulse tone 200 isochronic 10 amplitude 20

00:00:00 focus
00:00:30 focus

A custom waveform describes one cycle using evenly spaced amplitude points from 0 to 100. SynapSeq maps those points to the internal bipolar audio range and interpolates between them, including the connection from the final point back to the first.

Custom waveforms can be used anywhere a waveform is supported, including generated tones and waveform-driven effects on ambiance and music.

Definitions support between 2 and 16,384 points. The built-in sine, square, triangle, and sawtooth names remain reserved.

Custom waveforms can also be declared in .spsc files, making it possible to package reusable waveform definitions together with presets and templates.

Custom waveforms are not band-limited. Sharp corners and steep segments can introduce strong harmonics or aliasing, especially at higher carrier frequencies.

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Custom Transitions

Timeline interpolation is no longer limited to the built-in steady, ease-in, ease-out, and smooth curves.

The new @transition option lets a sequence define its own reusable interpolation curve:

@transition soft-land 0 2 12 42 78 96 100

focus
  tone 220 binaural 10 amplitude 20

00:00:00 silence soft-land
00:00:30 focus
00:05:00 silence soft-land

Transition points range from 0 to 100, must be non-decreasing, and describe the progression from the start state to the target state.

Custom transitions support between 2 and 256 points, with the first point required to be 0 and the last point 100.

They participate in normal compatible parameter interpolation and fades to or from silence. When a timeline transition uses steps, the custom curve is reapplied to each forward or backward leg.

Automatic boundary crossfades between incompatible channels remain linear.

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New shift Effect

v4.42.0 introduces the shift effect for tones, noise, ambiance, and music.

Unlike Doppler, which moves pitch by varying playback speed, shift applies an absolute frequency offset in opposite directions across the stereo channels.

shifted
  tone 300 effect shift 10 intensity 25 amplitude 20
  noise pink effect shift 8 intensity 20 amplitude 15

The declared value represents the total frequency separation. For example:

tone 300 effect shift 10 intensity 100 amplitude 20

shifts the wet left signal by +5 Hz and the wet right signal by -5 Hz.

intensity controls the dry/wet blend. At 0, the original signal is preserved. At 100, the output uses the fully shifted stereo pair.

The effect works on complete generated or external signals rather than simply detuning a carrier frequency, which makes it usable with complex sources such as noise, ambiance, and music.

@ambiance rain sounds/rain
@music meditation music/meditation

immersive
  ambiance rain effect shift 10 intensity 25 amplitude 30
  music meditation effect shift 8 intensity 20 amplitude 30

shift creates spectral divergence and stereo coloration. It does not guarantee a binaural beat or any particular perceptual response.

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Doppler for Music and Ambiance

The existing doppler effect now supports external music and ambiance tracks in addition to generated tones.

@ambiance rain sounds/rain
@music meditation music/meditation

moving-space
  waveform sine ambiance rain effect doppler 0.8 intensity 40 amplitude 30
  waveform sine music meditation effect doppler 0.8 intensity 40 amplitude 30

For external audio, Doppler varies stereo fractional playback speed while preserving the source's left/right relationship.

The effect rate is expressed in Hz, while intensity controls a playback-speed variation of up to approximately ±5% at full intensity.

A track's selected waveform controls the shape of the Doppler movement:

waveform triangle music meditation effect doppler 0.5 intensity 50 amplitude 30

Ambiance continues to loop while Doppler is active. Music remains finite and can finish slightly earlier or later because its playback speed changes over time.

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Independent Left and Right Amplitudes

Track amplitude can now be controlled independently for the left and right channels.

The existing single-value form continues to set both channels:

tone 300 binaural 10 amplitude 20

For explicit stereo control, use:

tone 300 binaural 10 amplitude left 20 right 10
noise pink amplitude left 30 right 25

The declared gains are applied after effects, so they control the final level of each output channel.

Inherited presets can also override channels independently:

base-focus as template
  tone 240 binaural 16 amplitude left 15 right 15

focus-left from base-focus
  track 1 left 25
  track 1 right 10

This makes asymmetric mixes possible without duplicating presets or relying on a pan effect, and left/right amplitudes interpolate independently during compatible timeline transitions.

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Faster WAV and MP3 Rendering

Audio rendering has been optimized in v4.42.0, reducing the time required to export SynapSeq sequences to WAV and MP3.

The optimization applies to the rendering/export path and requires no changes to existing SPSQ files or CLI workflows:

synapseq session.spsq
synapseq -mp3 session.spsq

Existing sequences remain compatible while benefiting automatically from the faster export pipeline.

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Upgrade Notes

• Existing .spsq files remain compatible with the new release.
• Built-in waveforms and transitions continue to work unchanged.
• @waveform and @transition definitions must appear with the other top-level options before preset or timeline content.
• shift is available for tone, noise, ambiance, and music.
• doppler is available for tone, ambiance, and music; noise does not support Doppler.
• The single-value amplitude <value> syntax remains supported and applies the same gain to both channels.
• WAV and MP3 exports automatically use the optimized rendering path without requiring sequence changes.

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This discussion was created from the release SynapSeq v4.42.0.