Sirens' Chor vs RasterFX
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Sirens' Chor
This experimental audio effect app analyzes input audio to generate a secondary harmonic voice using sine wave oscillators. The generated voice can be mixed with the original or played solo, creating a chorus effect. It's CPU intensive and operates within a specific frequency range.
- Harmonic analysis of input audio
- Sine wave oscillator synthesis
- Adjustable chorus effect
- Second voice generation
- AUV3 plugin support
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This one is quite experimental and CPU heavy app! While working on my Chord Detector app I came up with the idea to play the found harmonics with sine wave oscillators so I can hear what the algorithm is hearing :) It turns out to be an interesting output that led me to creation of this audio effect app. What happens here is that the input is analysed for main harmonics in the range of 80Hz to 1500Hz. Then a series of sine wave oscillators are set to play those harmonics with the exact frequency and volume and their output is added to create a second voice. This second voice can then be mixed with the input to create some kind of chorus or played alone. All this is CPU heavy process so it should be used with care... Also to make this effect possible I had to use limited range 80Hz to 1500Hz so it is not suitable for every instrument and you have to keep that range in mind when producing. Some very fast volume and frequency changes are applied to the oscillators. The app is AUV3
RasterFX
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Make any sound move. RasterFX is a playable modular multi-effects processor for iPhone and iPad. Use it standalone with a microphone, an imported audio file or built-in signals — or load it as an AUv3 audio effect in AUM, GarageBand, Logic Pro for iPad, Loopy Pro, Cubasis and other Audio Unit hosts. BUILD YOUR EFFECT CHAIN Choose from Filter, Delay, Drive, Reverb, Grain, Repeat, Motion and Dynamics. Arrange up to six plates in series or split them into parallel A/B paths. Reorder the chain and the sound changes with it. MODULATE ANY CONTROL Patch LFOs, envelope followers, random and chaos sources, step sequencers, MIDI, macros, the XY pad or device tilt to any control. Create up to 16 modulation lines, with live arcs showing exactly how the sound is moving. PERFORM THE PATCH Morph between four snapshots on the XY pad. Turn eight macros. Hold four momentary throws for stutter, sweep, reverse and freeze. RasterFX is built to be played with one hand, not programmed and left alone. GENERATE, LOCK, EVOLVE Nudge a patch, reshape it or roll a new one. Lock the parts you want to keep, undo any result and save the seeds worth returning to. Evolve lets the patch drift over time while staying anchored to the sound you chose. SEE WHAT YOU HEAR Every effect has its own live visualizer. The CRT and halftone interface makes filters, delay taps, grains, dynamics and modulation visible without turning the screen into a wall of meters. RECORD THE RESULT Record the processed output to WAV, rename takes and share them from the app. FREE TO START. PRO ONCE. Free includes all eight effects, all modulation sources, every factory preset, three plates, four modulation lines and 60-second recordings. No ads, account, watermark or reduced audio quality. RasterFX Pro is a one-time purchase — not a subscription. It unlocks six plates, 16 modulation lines, split routing, XY snapshot morphing, Evolve, A/B compare, unlimited recording length and your own saved presets. Your saved sound always plays back exactly as created, even if it uses Pro features; Free limits editing, never playback. Made for headphones, late at night.
Screenshots
Verdict
The clearest difference is price: RasterFX at Free against Sirens' Chor's $3.99. RasterFX also leads on rating (5.0 vs 4.0). Sirens' Chor's advantage is in-app purchases (none vs 1) and iOS requirement (10.0 vs 17.0). On ratings volume, ads and device support there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
RasterFX is free to download; Sirens' Chor costs $3.99 up front. RasterFX sells 1 one-off in-app purchase. Sirens' Chor asks for nothing beyond the download.
RasterFX holds the better App Store score, 5.0 against 4.0. Both are backed by a comparable volume of ratings — 2 and 1 respectively.
| Parameter | Sirens' Chor | RasterFX |
|---|---|---|
| Price | $3.99 | Free — better |
| Rating | 4.0 (2 ratings) | 5.0 (1 ratings) — better |
| Positive reviews | 100.0% of reviews | — |
| Number of ratings | 2 — better | 1 |
| Update frequency | Every 39 months | — |
| Ads | No | No |
| In-app purchases | No — better | Yes |
| Monetization | Paid | — |
| Devices | iPhone, iPad, iPod — better | iPhone, iPad |
| Requires iOS | 10.0 — better | 17.0 |
| Further details — not scored | ||
| Size | 11 MB | 5 MB |
| Age rating | 4+ | 4+ |
| Developer | Aleksandar Mlazev | Chih Han Lin |
In-app purchases
Sirens' Chor
No in-app purchases
RasterFX
- RasterFX Pro$3.99









