While there are a range of individual solutions to audio needs for the Pico, there isn't a framework, like Paul Stoffregen's Teensy Audio Library, for the Pi Pico.
This project aims to develop a flexible, event-triggered audio framework for the Pico on the Arduino-pico platform.

It initially aims to support
* I2S and TDM audio devices
* Simple synthesis (e.g. sine waves)
* Allow manipulation of audio signals (mixing, reverb, etc)
* Audio file play and record

Later, depending on contributor expertise, more functions may be supported
* FFT analysis
* USB audio
* Filtering (low-pass, high-pass, bandpass, etc)

The first draft of the platform specification is at https://github.com/palmerr23/PicoAudioFramework/tree/main/Framework

Discussion is encouraged at https://github.com/palmerr23/PicoAudioFramework/discussions