Playing music from your Mac

How it works

txMode listens to inputs — a mic, an interface, a mixer. Your Mac's own sound isn't one, so you need two small things to turn it into one:

• BlackHole — a free tool that acts like an invisible cable. Whatever you play into it comes out the other end as an input txMode can pick.
• A Multi-Output Device — a splitter, built into every Mac. It sends your sound to two places at once: your speakers, so you can hear, and BlackHole, so txMode can.

It takes about ten minutes, and you only set it up once.

Set it up (once)

1. Install BlackHole 2ch. Get it from existential.audio/blackhole — the site asks for your email and sends you the download link. Pick BlackHole 2ch and run the installer. It'll ask for your Mac password, and may ask you to restart.
2. Open Audio MIDI Setup. It's already on your Mac, in Applications ▸ Utilities — or press ⌘ Space and type its name.
3. Make the splitter. Click + in the bottom-left corner and choose Create Multi-Output Device.
4. Tick two boxes, in this order. First your speakers or headphones, then BlackHole 2ch. Tick Drift Correction next to BlackHole. The order matters — your speakers need to be the first one ticked.

Each time you broadcast

1. Send your Mac's sound to the splitter. In System Settings ▸ Sound ▸ Output, choose Multi-Output Device.
2. Pick BlackHole in txMode. Open Settings ▸ Setup, press Rescan if you need to, and choose BlackHole 2ch as the input. txMode remembers this for next time.
3. Play something. You should hear it, and the meter in txMode should move. Set your on-air level with the gain slider.
4. Turn on Do Not Disturb, then press Go Live.

When the show's over, set your Mac's output back to your usual speakers or headphones.

Good to know

• Your volume keys stop working while the Multi-Output Device is selected — that's a Mac limitation, not a fault. Turn it down on your speakers, or in the app you're playing from. The app's volume also changes what listeners hear, so set your on-air level with the gain slider in txMode.
• This carries your Mac's sound only, not your mic. To talk between tracks you'll need something that mixes the two — a small mixer or interface, or an app like Loopback (paid).
• Switching faster. Turn on System Settings ▸ Control Centre ▸ Sound ▸ Always Show in Menu Bar, and you can change your Mac's output from the top of the screen.

If something's off

• Flat meter while music is playing. Check your Mac's output is set to Multi-Output Device, and that BlackHole 2ch is ticked inside it. Your Mac treats BlackHole like a microphone, so txMode also needs microphone access: System Settings ▸ Privacy & Security ▸ Microphone, then quit and reopen txMode.
• The meter moves but you can't hear anything. Your speakers or headphones aren't ticked in the Multi-Output Device — open Audio MIDI Setup and tick them.
• BlackHole isn't in txMode's list. Press Rescan. If it's still missing, restart your Mac — the installer sometimes needs it.
• txMode can't open BlackHole. Make the sample rates match: check BlackHole's rate in Audio MIDI Setup (44.1 or 48 kHz) and choose the same one under Settings ▸ Setup in txMode.