On macOS 14.2 and later, DMXDesktop captures your Mac's own audio directly, with no extra driver to install.
Choose Default Output (Loopback) as the input in DMXDesktop's Audio Settings and Direct Audio Detection analyses whatever your Mac is playing, in real time. This is the same system audio capture Windows has had for about a year, so the two platforms now behave the same way.
It needs macOS 14.2 or later. DMXDesktop itself runs on macOS 14.0, so on 14.0 or 14.1 the option will not appear and you should use BlackHole as described below.
On macOS 14.0 or 14.1, or if you would rather route the audio yourself, install BlackHole, a free virtual audio driver. It is available at existential.audio/blackhole, or via Homebrew with brew install blackhole-2ch.
Once installed, create an aggregate device in Audio MIDI Setup (Applications → Utilities) combining BlackHole with your normal output. Select that device as the input in DMXDesktop's Audio Settings, and Direct Audio Detection will analyse anything playing on your Mac in real time.
Choosing your input device works properly from v1.0.52. Before that, the device you picked in Settings was stored but never bound to the capture, so audio detection always listened to whatever macOS had set as the system default input. If you concluded a particular interface did not work on your Mac, it is worth trying again.
macOS input devices also now offer the same left and right channel selection that ASIO has on Windows, set per device, so a multi-channel interface no longer has to send you its first two channels.