songsee is a single-binary Go CLI tool that turns audio files into spectral visualization images. It decodes audio natively (WAV, MP3) or via ffmpeg, computes an FFT specrogram, and renders nine visualiation modes (spectrogram, mel, chroma, HPSS, self-similarity, loudness, tempogram, MFCC, spectral flux) as a grid of heatmaps in PNG or JPEG format. The architecture is a monlith: the `cmd/songsee/main.go` entry point parsers flags using Kong, delegates to `internal/audio` for decoding, `internal/dsp` for signal processing (STFT, mel filtering, chroma, median filters, etc.), and `internal/render` for image generation. It produces deterministic output – same input flags yield identical bytes. The codebase is well-structured with comprehensive tests, CI/CD, and a clean separation of concerns. It demonstrates high craftsmanship in DSP optimization (e.g., bit-exact HPSS with median networks, tiling) and safe WAV parsing.