sonogram sg-1 

A scrolling sonogram for real-time frequency analysis.


Click to
 view full-size... Figure 1
Analysis of a Moog Voyager saw wave through a sweeping resonant LPF, with SG-1.
Clicking on the analysis window highlights Hz and dB values on the rulers.

SG-1 works in real-time. It continuously analyzes incoming data, and only stops when you freeze it. Both in frozen or running mode, every time you click or drag within the sonogram area, frequency and amplitude rulers highlight the values corresponding to that point.
A little LED-like screen shows you in detail analysis information and parameter modifications, or the transport position when idle.

Click to
 view full-size... Figure 2
With a different palette, we can highlight minimal noises and filter sweeps at the beginning of Depeche Mode's song:
"Only when I loose myself".

The unusual thing: it comes with six scientific color palettes (twelve considering they can be inverted, by clicking the palette twice), which can be switched on the fly. Each of them can highlight different dynamic ranges, from high power kickdrum beats, to little spikes coming out from the noise floor.
Every palette can be shifted by simply dragging the dB ruler, to better contrast the desired amplitude ranges.

Click to
 view full-size... Figure 3
Here's the zoomed trace of the legendary whistle from Ennio Morricone's soundtrack score: "Per qualche dollaro in più".

You can vary the number of taken snapshots-per-second on the fly, to increase or decrease the time resolution. At any time you can change the zoom ratio, without loosing in resolution over the signals which have already been analyzed. You can scroll the zoomed screen while analyzing, to easily locate the frequency range of interest.
A mark button is provided: it allows highlighting interesting parts of the waveform for subsequent individuation.

technical notes

  • Every editable parameter supports host automation
  • GUI resources are just loaded once, no matter how many instances you run in your host.

Some analyzer properties are hard-coded:

FFT Size 8192
FFT Window Function Blackmann
FFT Window Overlap 50%
Minimum spectrum power -96dB
Amplitude scale logarithmic
Frequency scale linear
Input signal stereo merge


  • Since this analysis plugin leaves unaltered the output signal, the process function bypasses the inputs and imediatley returns: every calculation is performed in a separate thread, to give priority to other effects in the chain.
  • I suggest to set your audio card's latency to values lower than 5ms, because high latencies will limit the smoothness of SG-1. In particular, you won't be able to use fast snapshots-per-second settings.


Win32  VST Sonogram SG-1 v1.0 (Win32 VST)