macOS still has no built-in way to send one app's sound into another: no record button for what your Mac is playing, no way to pipe app audio into a call. The classic answers are BlackHole (free, but you hand-wire multi-output devices in Audio MIDI Setup) or Loopback ($99).
SoundPipe is the middle: virtual audio devices with a UI where every route is a visible wire.
Create up to 16 virtual devices, rename and resize them (2 to 64 channels) live
Capture any app, all system audio, or any mic or input
Per-channel volume with live meters on every wire
Monitor through your headphones or speakers while you route
Any sample rate, under 15 ms latency
One-click driver install: no Terminal, no kernel extensions
$10 once, up to 3 Macs, no subscription, no account. The trial is the full app in 20-minute sessions you can restart forever.
If BlackHole already covers what you need, keep using it. There's a comparison on the site that says exactly that.
