Honest comparison · Updated 2026-06
PaulXStretch vs Reverie
Both tools share a common ancestor in Paul Nasca's Paulstretch algorithm. But they solve very different problems. Here's a respectful, detailed breakdown to help you pick the right tool for your workflow.
A shared origin: Paul Nasca's algorithm
In 2006, Romanian engineer Paul Nasca published Paulstretch, an open algorithm for extreme time-stretching based on phase randomization in the frequency domain. Unlike conventional time-stretching methods that try to preserve transients, Paulstretch deliberately embraces spectral smearing, producing the lush, infinite pad sounds the ambient community has loved ever since.
Paulstretch was made famous by the viral "Justin Bieber 800% slower" experiment, which revealed just how beautiful ordinary pop could become when stretched into a 35-minute cathedral of sound.
The algorithm became a reference point for ambient producers. PaulXStretch was created by Xenakios as an extended cross-platform GUI port of Paulstretch, and maintenance was transferred to Sonosaurus (Jesse Chappell) in April 2022. It runs on macOS, Windows, Linux and iOS, as a standalone application and as a plugin (AU, VST3, AAX, CLAP, AUv3), and remains free and open-source under the GPL license. It is the de-facto reference implementation today.
Reverie builds on the same lineage. Dreamtime, our own evolution of the Paulstretch algorithm, is one of 37 DSP modules inside a cohesive native macOS and Windows app. We are not a PaulXStretch clone, and we do not compete with it: we serve a different workflow. Both tools coexist happily in many studios.
What Dreamtime adds on top of Paulstretch
Dreamtime is not a direct port of the 2006 algorithm. It is a native C++ implementation with six engineering signatures that turn a classic "frozen drone" generator into a living, production-ready soundscape engine. Every decision is documented in our engine source.
Spectral Drift
The read head wanders through the source following three sinusoids at golden-ratio frequencies (phi, phi squared) with plus-minus 30% drift. Paul Nasca reads linearly. This is the #1 lever for hour-long renders that stay alive instead of turning static after a minute.
Stochastic Multi-Segment
For sources over 3 seconds, Dreamtime extracts 2 to 4 non-contiguous micro-segments, crossfades them, and detects silent zones with retry logic. Paul Nasca extracts a single contiguous segment.
Phase Continuity Blending
Instead of pure per-frame random phases, Dreamtime blends 70% new randomness with 30% of the previous frame using shortest-arc wrapping. Reduces the grainy digital artefacts of the original while preserving the drone character.
Adaptive Segmentation
Segment duration auto-scales with source length: 40 to 70% for sources under a second, down to 20 to 40% for 30 to 60 second sources. Always guarantees at least 40 FFT frames. Paul Nasca required a fixed duration.
Engine-Level Duration Correction
A post-chain orchestration loop guarantees exact output duration: pre-loop, re-stretch, and 3.5s sigmoid fades. Paul Nasca is single-pass with no feedback. This is what makes Dreamtime suitable for production exports locked to target durations.
Seeded Phase RNG
A dedicated MT19937 instance handles phase randomization, isolated from the segment-selection RNG. You can lock the drone texture and vary the upstream chain without the phase character shifting underneath.
The FFT, Hann window, and overlap-add are standard – as they should be. What we built on top is where Reverie's signature lives. Paul Nasca invented the technique. Dreamtime is our evolution of that technique for modern studio work.
What PaulXStretch excels at
PaulXStretch is a formidable open-source tool that continues to serve the ambient community after years of use. It stays true to the original Paulstretch vision and does one thing exceptionally well.
Pure Paulstretch, refined
Careful parameter controls, optional frequency shift, compressor, and onion layers. A faithful, polished take on the original algorithm.
Free, open-source, cross-platform
GPL-licensed. Runs on Windows, macOS, Linux and iOS, as a standalone app and as a plugin (AU, VST3, AAX, CLAP, AUv3) you can drop directly into any modern DAW.
Extreme stretch ratios
Stretch factors in the hundreds or thousands are perfectly usable. If you want to turn a 3-second sample into a 3-hour drone, PaulXStretch handles it without complaint.
Community-supported, auditable code
Open GitHub repository. You can read the code, contribute, fork, or build custom variants.
PaulXStretch is the right choice for:
- •Musique concrète purists and academics studying the original algorithm
- •Producers who already own a full DAW toolkit and just need a clean stretch tool
- •Linux or iOS users (Reverie is macOS and Windows only)
- •Plugin-based workflows where Paulstretch needs to live inside a DAW session
- •Archival and experimental stretching where no other effects are needed
What Reverie brings
Reverie is designed to get you from a source file to a finished ambient soundscape in one click, and to a fully customized one in a few more. Dreamtime is just one ingredient in a larger recipe.
37 DSP modules, one cohesive app
Dreamtime (our extended Paulstretch), spectral freeze, shimmer reverb, spectral cross-synthesis, formants, resonators, polyrhythm tremolo with 12 presets, chord layer with 16 voicings, and more.
20 curated factory presets
Turn-key ambient signatures: Infinite Drone, Cathedral, Deep Ocean, Harmonic Healing, Tape Memories, Forest Breathing, DNA Splice, Ancient Chant. Pick a mood, press Generate.
Pro Chain Builder
Drag any of the 37 modules into your own effect chain. Reorder, tweak every parameter, save your chains as custom presets. Full Undo/Redo history.
Finished-ready output
4 export formats (WAV, FLAC, OGG, AIFF) at 16 or 24-bit. Deterministic seed for bit-perfect reproducibility.
Reverie is the right choice for:
- •Producers and musicians who want finished soundscapes, not raw material
- •Game composers needing endless, non-looping background beds up to 30 minutes long
- •Sound designers looking for a broader DSP palette beyond pure paulstretch
- •Content creators wanting royalty-free ambient for videos and podcasts, delivered fast
- •Anyone who prefers presets and curated workflows over deep parameter tweaking
Feature-by-feature comparison
Updated June 2026. Based on PaulXStretch 1.6.x and Reverie 1.13.
| Feature | PaulXStretch | Reverie 1.13 |
|---|---|---|
| Price | Free / donationware | Free (3-min) · 29€ unlimited |
| License | GPL open-source | Proprietary, commercial output OK |
| Platforms | Win / Mac / Linux / iOS | Mac + Windows (native) |
| Plugin formats | AU, VST3, AAX, CLAP, AUv3 | Standalone only |
| Core stretch algorithm | Paulstretch | Dreamtime (extended Paulstretch) + 36 other DSP modules |
| Max stretch ratio | Very high (hundreds) | 100× |
| Max output duration | Unlimited | 30 min Pro · 3 min Free |
| Factory presets | None (parameter-based) | 20 Pro + 5 Lite Free |
| Curated artistic styles | N/A | 22 styles |
| Custom effect chain builder | No | Yes (Pro mode) |
| Input formats | WAV | WAV, MP3, FLAC, AIFF, OGG, M4A |
| Output formats | WAV | WAV, FLAC, OGG, AIFF (16 or 24-bit) |
| Spectral freeze | Built-in | Dedicated module + shimmer integration |
| Shimmer reverb | Via DAW plugin | Built-in |
| Formant filter / resonator | No | Yes (8 vowels, 12 presets) |
| Seed-based reproducibility | N/A | Yes |
| Community and support | GitHub issues, forums | Email + Discord |
Same source, two outputs
Imagine you drop a 30-second vocal take into each app and ask for a 5-minute meditative drone.
PaulXStretch workflow
Open PaulXStretch, load the file, set stretch to ~10×, tune window size and frequency controls, render. Then drop the output into your DAW, add a shimmer reverb plugin, EQ out the high-frequency smear, automate the wet/dry, print the final take. Total time: 15-30 minutes once you know the ropes, longer while learning.
Reverie workflow
Drop the file into Reverie. Click "Harmonic Healing" (a Pro preset built for this exact use case). Set target duration to 5 minutes. Click Generate. Export as 24-bit FLAC. Total time: under a minute. If you want to customize further, switch to Pro Chain Builder and tweak specific modules.
Pricing and licensing
PaulXStretch
Free / donationware. GPL license. You can use the app commercially; Sonosaurus accepts optional donations. The GPL license applies to the software itself, not to your audio output – you retain full rights over what you create.
Reverie
Free up to 3-minute exports, 29€ one-time for unlimited length, all presets, Pro Chain Builder, and 4 export formats. No subscription, ever. Lifetime updates for the 1.x series. You retain full rights over your output; we claim nothing.
Both tools let you use the output in commercial productions, provided you have the rights to your source audio. Your work remains yours.
When to pick which
Short decision matrix if you're unsure.
Pick PaulXStretch if
- ✓You already live in a DAW and need an AU, VST3, AAX or CLAP plugin
- ✓You are on Linux or iOS
- ✓You want pure Paulstretch with full parameter control
- ✓Open-source and auditable code matters to you
- ✓You are researching the algorithm itself
Pick Reverie if
- ✓You want finished soundscapes in one click
- ✓You need 37 DSP modules beyond pure stretch
- ✓You compose for games, film, or content and need volume + speed
- ✓You prefer curated presets over deep parameter tweaking
- ✓Native performance and a polished UI matter to you
- ✓You want Undo/Redo and seed reproducibility
Can they coexist?
Yes, happily. Many users keep PaulXStretch for pure stretch experiments and reach for Reverie when they need a finished ambient piece. A typical hybrid workflow:
- 1Capture your source material (field recording, vocal take, synth stem)
- 2Use PaulXStretch inside your DAW session for experimental extreme stretches
- 3Use Reverie standalone when you need a finished, multi-effect soundscape at export quality
- 4Drop both outputs onto your DAW timeline and layer as needed
Frequently asked
Is Reverie a PaulXStretch clone?
No. Dreamtime – our extended take on the Paulstretch algorithm – is one of 37 modules in Reverie. The UI, the architecture, the presets, the Pro Chain Builder, and the rest of the DSP are all original work. PaulXStretch and Reverie share ancestry with Paul Nasca's algorithm, not code with each other.
Can I import my PaulXStretch presets into Reverie?
No. The preset systems are not compatible. You can recreate similar results in Reverie's Pro Chain Builder by chaining Dreamtime with Reverb and other modules.
Which one runs better on older Macs?
Both are native and reasonably lightweight. Reverie runs natively on Apple Silicon and Intel. PaulXStretch also has native builds. Performance differences are minimal on modern machines; for 10-year-old hardware, PaulXStretch's simpler UI may feel snappier.
Is Reverie open source?
No. Reverie is proprietary. The code is not published. We credit the academic research that informs parts of our DSP (Nasca, Smith, Truax, Laroche/Dolson) but the implementations are our own.
Does Reverie ship as a DAW plugin?
Not yet. Reverie is currently standalone only. Integration with DAWs is done via file export (drag & drop supported).
Our recommendation
If you want a free, open-source paulstretch that lives inside your DAW, PaulXStretch is the right tool. It has served the ambient community beautifully for years and we respect it enormously. If you want a cohesive, finished ambient soundscape studio with 37 DSP modules, curated presets, and native performance on macOS and Windows, Reverie is what we built for you. Try both – they solve different problems, and many producers keep both at hand.