Hi Jerome,
I just wanted to let you know that I figured out a way to make this work. It requires the free SoX audio tool.
I downloaded this to c:\sox-14-3-2\sox.exe and made another copy of this executable, called "play.exe", in the same directory.
Now using setWavPlayer("c:\sox-14-3-2\play") will allow listen() to work without popping up a GUI. This also works for play() in tuneR.
Note that using setWavPlayer("c:\sox-13-3-2\play.exe") will NOT work, because the sox program changes its behavior based on invocation name. SoX is historically a UNIX program, and it doesn't recognize "play.exe" as being the same as "play".
best,
jesse