It's a command line program written in C that converts plain text messages into .wav files, enabling you to hide messages within sound clips such as music.
Clone the repo with git clone git@github.com:ZoeB/steg.git, go into that directory with cd steg, compile the program with make, and run it with a message you'd like to encode, such as ./steg 'Foo'. Steg will create a new file, out.wav, with your message encoded in it.
There are various command line arguments available. Run ./steg without a message for a list of them.
With a spectrogram of the waveform. There are many ways of generating a spectrogram. As an example, I'd recommend Spek.
The bulk of the program was written by Zoë Blade. The .wav file writing routine was written by Douglas Thain.
It's released under the CC BY 4.0 license.