A new spectral synthesizer has landed on the App Store, and it arrives with expressive control in mind. SpectraPad, from developer 4Pockets, is a hands-on synth for iPadOS and macOS that, according to Synth Anatomy's coverage, has "MPE and MIDI CC support" onboard. It is available now on the Apple App Store for 9.99 euros.
What SpectraPad Does
At its core, SpectraPad is an additive-style spectral instrument. The sound is built from 16 harmonic partials, each with its own slider, so you shape the timbre by drawing a spectrum rather than choosing a waveform. Around that core sit a subharmonic section and a harmonics section, plus a one-knob formant control that moves through vowel qualities (A, E, I, O, U).
A scale function lets you constrain playing to a chosen scale, which is handy on a touchscreen. The sound then passes through a multimode filter with morphing, and a modulation engine with ADSR envelopes and LFOs. Many parameters are automatable, which matters if you plan to record performances in a DAW.
The effects section is generous for the price: stereo delay, stereo echo, cloud effects, a stereo arpeggiator and gate effects.
Standalone and AUv3
SpectraPad runs as a standalone app and as an AUv3 plugin, on both iPadOS and macOS. That makes it usable inside any host that supports AUv3 instruments. If you are new to hosting expressive plugins on iPad, our guide to MPE on iPad and AUv3 hosts covers the setup details.
Why MPE Matters for a Spectral Synth
Additive and spectral engines are a natural fit for per-note expression. When every note is a stack of partials, small changes in pressure or vertical finger position can reveal or hide upper harmonics in a very musical way, much like bowing closer to a string's bridge. With MPE, each note travels on its own MIDI channel, so pressure, slide and pitch bend can affect one note without touching the others.
The source article confirms MPE support but does not detail which parameters respond to which gestures, so we cannot say yet how deeply the expression is wired into the engine. Before you buy, test how the formant control and partial levels respond to your controller. If your controller sends slide as CC74 and pressure as channel pressure, as most MPE devices do, those are the two messages to try first. For background on that mapping, see our explainer on MPE slide and CC74.
Who It Suits
At under ten euros, SpectraPad is a low-risk way to try spectral synthesis with a touch controller. It should appeal to sound designers who like building timbres from the ground up, and to iPad players who want an expressive voice for ambient or textural work. It is less likely to replace a full-featured flagship synth, but that is not its aim.
Practical Tips
- Check your pitch bend range. MPE member channels commonly use a range of 48 semitones; a mismatch makes glides sound wrong. Our pitch bend range fix explains how to diagnose it.
- Enable MPE in the host or controller. Some setups need MPE mode switched on explicitly before per-note data arrives.
- Record the MIDI. Capturing the expressive data lets you re-edit gestures later instead of committing to audio.
Where to Get It
SpectraPad is on the Apple App Store. The article we reference did not link to a dedicated developer website, so the store page is the best official source for system requirements and updates.
It is encouraging to see MPE listed as a standard feature on a ten-euro app. A few years ago, per-note expression was a premium selling point; now it is increasingly part of the baseline for new synths. For players with MPE controllers, that means a steadily growing library of instruments ready to respond to touch.