# Saeternesdaeg — Feedback Wavefolding Synth

> Feedback Wavefolding Synth (iPhone/iPad app by Kei Odaka.)

- Source: https://appshunter.io/ios/app/saeternesdaeg/id6807687659 (this page in markdown: same URL + `.md`)
- Developer: [Kei Odaka](https://appshunter.io/developer/6807615300)
- Category: Music
- Price: $4.99 (on sale, was $5.99)
- Age rating: 4+
- Requires: iOS 18.0 · 2 MB
- Languages: American English
- Released: 2026-09-24
- Data updated: 2026-10-17

## What is Saeternesdaeg?

One oscillator. Four shaping stages in series. Everything you hear comes out of that single chain folding back on itself.

TZFM is a through-zero FM oscillator. Push the linear FM deep enough and the phase increment goes negative — the phase actually runs backwards, and the tone breaks into sidebands that a normal FM oscillator cannot reach.

FOLDER squares up whatever crosses its threshold into an asymmetric pulse, then fills the inside of that pulse with reflections. Pulse width and phase are the two axes.

PULSES is a chain of comparators slicing the waveform into one to five pulses per cycle. It divides without tracking pitch, so the result is a hard, metallic harmonic series rather than a transposition.

XOR compares the pulse output against the feedback sum and judges it by amplitude, not polarity — the classic analogue exclusive-or, which turns two simple shapes into a dense, unpredictable third.

After the chain: a third-order filter and a fourth-order chaos oscillator for slow, never-repeating drift.

Four XY pads drive the stages. Each pad records and replays your finger. The camera can take over the pads — brightness and movement in the frame become the pointer — and device tilt rolls a gravity ball inside each pad. Presets, a sequencer, chorus, reverb and glide are there when you want the instrument to keep moving on its own.

Every stage follows a circuit designed by Ian Fritz and published on his own site, used here with his permission. Sæternesdæg is independent software, not affiliated with, sponsored by, or endorsed by him.

Landscape only. Nothing leaves the device: no accounts, no network, no analytics. Camera frames are read and discarded, never stored or transmitted. Headphones or a decent speaker recommended — a lot of this instrument lives in the low end.

## Is Saeternesdaeg safe?

Not enough ratings yet to assess Saeternesdaeg.

## Is Saeternesdaeg legit?

Saeternesdaeg appears legitimate, with a few gaps. The AppsHunter Legitimacy Score for Saeternesdaeg is 65 out of 100 points across 7 verification signals from App Store and developer data.


## Version history (last 3 releases)

### 1.1.2 — 2026-09-28

The four corner keys now carry their names, laid out beside the icons so the rows keep their height. The upper and lower sliders share one size and one position, and the pads are drawn as a plain frame. Engraved lettering is now orange.

### 1.1.1 — 2026-09-25

Small fixes and refinements.

### 1.0 — 2026-09-24

No release notes.

## More apps by Kei Odaka

- [Sunnandaeg](https://appshunter.io/ios/app/sunnandaeg/id6807615298)
- [Ferrec](https://appshunter.io/ios/app/ferrec/id6807860695)
- [VGACam](https://appshunter.io/ios/app/vgacam/id6813754422)
- [Frigedaeg](https://appshunter.io/ios/app/frigedaeg/id6813849843)
- [Thunresdaeg](https://appshunter.io/ios/app/thunresdaeg/id6813862696)

All apps by Kei Odaka: https://appshunter.io/developer/6807615300

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-10-17.*