Jörg Bitzer is offering two freeware analysis VST plug-ins for download: IHASpectrogram and IHASpatialAnalyzer.
IHASpectrogram is a tool developed to analyze the frequency content of an audio signal. It shows you the strength of a frequency over the time. The strength itself is coded in colours.
The application areas are manifold. Sound engineers and audio researcher use a spectrogram to find the pitch frequency of an instrument, to find annoying single tones, to show the effect of different dither and noise-shaping algorithms, or just to see, if a mix is well balanced in its frequency behaviour.
IHASpatialAnalyzer is a new method to display the stereo behaviour of audio material over time. It is based on the data of a vector-scope or gonioeter, but displays the results differently. You should be familiar with the vector-scope in order to be sure, what can be seen with this tool. IHASpatialAnalyzer can be used for the analysis of impulse responses of reverberation units.
Both plug-ins are available for Windows PC.