Friture - Friture is a program designed to analyze audio input in real-time.
Audacity - Audacity is a free and open-source audio production software suite that includes a surprising array of editing tools and recording systems.
Visual Analyser - A powerful software implementing a Spectrum Analyzer, Oscilloscope, Frequency meter, Distorsiometer, Volt meter and more... plus complete D/A conversion, ZRLC, Impedance meter
FL Studio - Image-Line's FL Studio, now on it's 12th version, is a well-known music production suite and the most popular beat processor on the market, due no doubt to its longevity. Read more about FL Studio.
xoscope - Xoscope uses the input of your Sound Card, EsounD and/or a ProbeScope/osziFOX and Bitscope-Hardware.
Reaper - Reaper is a focused digital audio workstation (DAW) developed by Cockos. In the creation of the software, the digital audio technology company intended to make audio editing accessible to the masses.