Music & Acoustics
Spectrogram of a Chirp
frequency rising with time

A time-frequency heat map of a rising chirp: the bright diagonal ridge is instantaneous frequency climbing as the sweep rate increases.
Computed & rendered in pure C# on the frozen OnlyCSharp 1.8 library — animation baked to GIF with the library's own
Gif encoder (no GPU, no ffmpeg, no external packages).