This software is a free download and is very interactive and easy for students to use. The fundamental frequency can be manipulated, as well as how many harmonics are present. Two time windows show the composite waves present as well as the combined complex waveform. Another window shows the FFT analysis of the complex wave. The tones present can be heard as well as seen. A second menu option allows for the introduction of external input for analysis. Very versatile and fun! My students love it!