True Audio: Audio Spectrum Analyzer and Loudspeaker Design Software
DL4YHF's Audio Spectrum Analyser
Add-on: Spectrum Analyzer and Graphic Equalizer, Total Recorder - captures any audio from the Internet, records audio from CD, microphone, line-in, converts any sound formats to WAVE file. Phone recording system.
Blue Cat's FreqAnalyst - Real Time Spectrum Analysis Plug-in (VST, Audio Unit, VST3, AAX) (Freeware)
Audio Test Set
SpectrumAnalyzer | Details | SIR Audio Tools
Blue Cat's FreqAnalyst Pro - Real Time Spectrum Analyzer and Audio to MIDI AU, RTAS, DX and VST Plug-in