4Pockets SpectraPad: a $9.99 spectral synth for iPad
4Pockets has released SpectraPad, a spectral synthesizer for iPad that builds sound from its harmonics, aimed at pads and textures. Who it is for, what it costs, what it competes with.
UK developer 4Pockets released SpectraPad on November 1: a spectral synthesizer for iPad, priced at $9.99 on the App Store. The app has a clear target: pads, evolving textures and atmospheres.
Spectral synthesis in one sentence
A periodic sound breaks down into harmonics (or partials), sine waves at multiples of the played pitch. Spectral synthesis, a close cousin of additive synthesis, builds sound by setting those harmonics directly, instead of starting from a ready-made waveform and filtering it. As 4Pockets puts it in its listing, the waveform becomes “the result” of what you do to the spectrum.
What the app includes
The official App Store screenshot shows the architecture:
- 16 harmonic sliders, with distribution presets (saw, square, triangle, pulse, random, gaussian) and global controls to tilt (Curve), balance (Balance) and concentrate (Focus) energy across the spectrum;
- a formant control with A, E, I, O and U vowels for voice-like tones, a subharmonic to add low-end weight, and an inharmonicity setting for bell-like sounds;
- a 12 dB filter with resonance and morphing, with its own envelope;
- an ADSR amp envelope (attack, decay, sustain, release: see our ADSR explainer) and LFOs routed to filter, amp and pitch;
- an arpeggiator, a rhythmic gate effect, plus chorus, echo, reverb and “cloud” (granular smear) effects;
- an MPE button (MIDI Polyphonic Expression, which gives each note its own modulation on compatible controllers).
What the listing does not say
The App Store listing requires an iPad on iPadOS 15 or later; on Mac it runs on Apple M1 or later, but Apple notes it is “designed for iPad” and “not verified for macOS”. It does not mention an AUv3 version (the iOS plugin format that lets a synth load inside a host or DAW). Synth Anatomy reports the app runs standalone and as AUv3: worth checking in your host before relying on it.
Who it is for, what it costs, what it competes with
Who it is for. iPad musicians on the move who want pads and textures rather than punchy basses or leads, and anyone curious to hear what harmonics do to a timbre by moving them one by one. Sixteen harmonics is a modest count for detailed resynthesis, but enough for pads and bell tones.
What it costs. $9.99 on the App Store (€9.99 in Europe), version 1.0, with no in-app purchase listed.
What it competes with.
- Moog Animoog Z: an MPE-capable wavetable synth for iPad that moves playback through a space of waveforms rather than setting harmonics.
- AudioThing Materia: additive resynthesis that turns a recorded sound into an additive patch (see our Materia article). It starts from analysing an existing sound, where SpectraPad starts from a blank page.
For a related approach that stacks operators rather than harmonics, see our FM synthesis guide. More iPad and mobile releases are in our mobile apps section.
