Read a wave file that contains two sinusoids, 7kHz and 11.025kHz (=44.1kHz/4), and display the waveform and its spectrum.
Here I used the libraries, OpenGL, GLUT and FFTW3, all popular for UNIX environment. With OS X, perhaps I should do otherwise.
You can find the source code at this point of the history at: https://github.com/jh1ood/libsndfileXcode/blob/be835c328d8c032a242094d809599208276fdee8/libsndfileXcode/main.c.