This program samples data from the line-in of the soundcard. The callback then invokes a function to apply Fast Fourier Transforms (FFT) to the sampled buffer. The frequency domain is then rendered on a GDI surface using a polyline. The goal of that software was to monitor the frequencies variations between the 300Hz and 3.3KHz coming out of a telephone. This project was then used to experiment with basic voice recognition by comparing the real-time input stream with pre-sampled frames.