Just A Byte

Using 8bpp bitmap image format and Unsigned 8-bit PCM audio format means that one byte of data is also one pixel and also one audio sample.

1. Open an image in GIMP
2. In the main window menu choose File - Open As Layers and your audio as image file
3. In the Layers window reduce the Opacity of the upper layer
4. The bytes which represent the audio layer are now mixed up with the the bytes of the image layer. Favour the audio! It is easier to look at an ugly image for a while than it is to listen to bad audio.
5. Export as raw format 8bpp

You now have a bitmap file you can listen to.