Setting up a wav-controlled voltage source is as simple as right-clicking on the value of the source ('V' by default), and changing it to
path\to\inputfile.wavis the path to the file and
Nis the channel that you want to use, starting from 0. So
Nwould be 0 if you want to use the left channel of a stereo file. In Windows, you can just put the filename or a relative path and LTspice will look in the directory of the top-level schematic. In WINE this doesn't seem to work so well, and you need to put an absolute path.
To create an output .wav file, you'll need the
.WAVESPICE directive. To create a 16-bit file sampled at 44100 samples per second, you would place this:
.wave "path\to\outputfile.wav" 16 44100 NODE
path\to\outputfile.wavis where you want to write the file, overwriting any other file with the same name.
NODEis the name of the node that you want to use as the output.
For this simulation you'll want to use the Transient simulation type. This is the mode that simulates and plots your circuit over time. To use it, open the "Simulate" menu and choose "Edit Simulation Command." Select the leftmost tab, called "Transient," and fill in the start and end times. As far as I know, you should be able to leave the step time blank, and LTspice will figure it out.
After running the simulation, you should have an output .wav file that you can listen to in your favorite media player. Enjoy.