PhonoPaper is described as 'camera app for playing pictures with encoded sound (PhonoPaper-codes). With this app, you can also create your own codes: 10 seconds of sound can be recorded from a microphone and converted into an image' and is a Audio Editor in the Audio & Music category. There are three alternatives to PhonoPaper for a variety of platforms, including Windows, Mac, Android, iPad and iPhone. The best alternative is Photosounder, which is free. Other great apps like PhonoPaper are Virtual ANS (Free) and spectrogram (Free, Open Source).
Photosounder is the first audio editor/synthesizer to transform any sound as an image and to create any possible sound from an image. It have an entirely image-based approach to sound creation and editing.
Virtual ANS is a software simulator of the unique Russian synthesizer ANS - photoelectronic musical instrument created by Evgeny Murzin from 1938 to 1958. The ANS made it possible to draw music in the form of a spectrogram (sonogram).