RoEx Audio has introduced Phosphor, a new software instrument for macOS that uses spectral synthesis to convert images into audio.

Spectral synthesis is very different from other types of synthesis. It builds on the idea that audio can be represented as a spectrogram, an image where time runs left to right, frequency runs bottom to top, and brightness represents loudness. A bass note is a bright horizontal line near the bottom. A siren is a diagonal streak. A snare is a vertical column.

Instead of converting audio into a picture, though, Phosphor inverts this and turns pictures into sound. You can ‘paint’ directly on to the spectrogram, or load an image, and Phosphor will synthesize audio from it.

Because of the nature of this approach, Phosphor is probably best suited for sound design – creating textures, drones and soundscapes – that you then export for use in your DAW.

Here’s an example of Phospor in action:

Features:

• Spectrogram Canvas – Draw directly on a frequency-vs-time canvas. The vertical axis follows a logarithmic scale mapped to musical octaves, so equal distances always equal musical intervals. Includes piano roll overlay, beat grid, and snap-to-note.
• Colour Mode – In standard mode, brightness controls loudness and every frequency is a pure sine. In colour mode, hue shapes the timbre, red produces sawtooth-like warmth, green gives square-wave hollowness, blue creates soft flute-like tones. Saturation controls harmonic intensity.
• Four Synthesis Engines – Choose how your spectrogram becomes sound.
• STFT for classic spectral synthesis with iterative phase reconstruction.
• Additive for clean, precise oscillator-bank synthesis.
• Noise Band for textural, granular results.
• Blend to mix tonal and noise components.
• ADSR Envelope – Shape the amplitude dynamics of your sound with a full attack-decay-sustain-release envelope. Visualize the envelope shape in real time as you adjust parameters.
• Image Sonification – Load any photograph, painting, fractal, or generated image. Phosphor maps the visual composition to audio, brightness to loudness through a perceptual dB curve, vertical position to pitch, horizontal position to time.
• Flexible Export – Export in WAV, AIFF, FLAC, or MP3. Choose 16-bit, 24-bit, or 32-bit float at 44.1kHz or 48kHz. Optional peak normalisation. The exported audio uses iterative phase reconstruction for clean results.

Availability:

Phosphor is available now as a free download, no account required.