PAPU, initially released in 2017 is a free 8-bit chiptune Synthesizer plugin by Soca Labs and now available as a free AUv3 app for iPad.
The latter, i.e. PAPU, is now available as a free AUv3 Ssynthesizer for iOS
SocaLabs PAPU is an 8-bit chiptune Synthesizer that emulates the hardware sound engine of the Nintendo Gameboy. It has 8 voices of polyphony, offers two square wave channels, sweeps on the first square wave channel as well as a noise generator. Each channel has two switches that let you activate the l & r channels individually. Operation in mono or stereo, it’s your choice. A nice addition is the waveform display on the right side that gives you a representation of the actual waveform.
As I said before, the app is also available as a free plugin for PC (VST 32-/64-bit) Mac (VST/AU 32-/64-bit), and Linux. Further, the code of the synth is open-source so you are able to modify it and create a bigger app out of it.
It’s not a revolutionary new iOS synthesizer app, but hey, it a free AUv3 Synthesizer for iPad. One more sound generator for your arsenal and all this free of charge.