Pydub is a mature, high-level Python library for audio manipulation. It provides an immutable `AudioSegment` class that supports slicing, concatenation, overlaying, gain changes, fading, and format conversion using ffmpeg/avconv as a backend for non-WAV formats. The library includes a variety of DSP effects (normalize, speedup, compression, filters, equalization), silence detection/splitting, signal generators (sine, square, sawtooth, white noise), and optional playback via simpleaudio, pyaudio, or ffplay. Its architecture is modular, with core functionality in `audio_segment.py` and effects registered via a decorator pattern. The codebase demonstrates clean abstractions and is well-tested, though it carries some legacy Python 2 compatibility patterns.