Record and playback with 24 bit resolution using high resolution sound cards. You asked for a more extensive FFT Spectrum Analysis tool. Choose wire-mesh or solid forms, color coded intensities, contours, log or linear frequency, normal or dB amplitude, etc. Zoom, pan, and scroll with the mouse. When you're done, you can print the graph or save it as a JPEG or BMP file.
Any previous point is just a single mouse click away.
Of course, the undo depth is completely programmable so you can optimize it for your system. Clean them up with this. One application and nobody will ever know that your little brother used to put a quarter on the tonearm. Also known by the names Acoustical Modeling and Ambience Modeling. This is a great way to get realistic reverb sounds or to emulate musical devices.