CortexDJ is desktop DJ software that works from a folder of music you own. It analyzes key, BPM, energy and structure on your computer, picks and orders the tracks, beatmatches them and renders a finished set to WAV or FLAC. It works with local files only, not streaming services. Sets can also be exported to rekordbox, Serato, VirtualDJ, Traktor, Engine DJ, Mixxx or djay. The site states CortexDJ is not affiliated with those apps, and music is processed locally and never leaves your computer.
The Free edition ($0) covers analysis, Simple and Advanced modes, rendering and export. The first set needs no key, and later sets need a free key covering 2 computers. Pro is $59 per year or $4.92 per month and adds MIDI controllers, audio and video recording and live-streaming. Lifetime is $127 one-time, with a 30-day money-back guarantee. It runs on Windows 10/11 64-bit (the installer is unsigned, so SmartScreen shows a warning) and, as a beta, on macOS Apple Silicon only.
The builder wanted a finished DJ set from their own music, made on their own computer, without a streaming service in the middle.