Under The Microscope

Halloween Fun with Farrago and Airfoil

Before it was even October, my kindergartener son decided we ought to decorate for a truly spooky Halloween. Our concept: a scary cauldron which kids reach in to to retrieve their candy, complete with smoke and lights.

I took it upon myself to start on the (often overlooked) sound design. Spooky audio is an important component of any scary display or haunted house, and with today’s portable speakers, it’s easy to add. I’ll be placing a couple of small wireless speakers outside to play music and scary sound effects. As you might have guessed, I plan to use Rogue Amoeba apps to help.

Making Background Music

First up, we need some creepy ambient music. Finding something pre-made online is easy, but it’s even more fun to make this ourselves. I previously used GarageBand to make the example music loops we ship with our soundboard app Farrago, so I knew it would work well here too.

I started by making a new GarageBand project in a minor chord, and set the tempo to the slowest possible speed, five beats per minute (BPM). Then I added a bunch of loops and turned up the reverb. In about half an hour, I had made a pretty decent backing track. Almost everything sounds creepy at five BPM, so a little trial and error should be enough to arrive at something suitably unsettling.

Everything sounds eerie with these settings in GarageBand.

Samples like Bells, Choirs, Pads, Organs, and Vox all seem to work well. On top of that, the pitch-shift, echo, and reverb filters are useful to make them sound extra spine-chilling.

I encourage you to experiment and make your own audio, but you’re also welcome to use my audio file.

Here’s a short excerpt so you get the idea:

To get the whole file: Click to download (15 minutes, 11 MB)

Setting Up Sound Effects with Farrago

The music will serve as a backdrop, but I also want to be able to play spooky sound effects on demand. Here’s where our soundboard app Farrago comes in. I downloaded a bunch of sound effects from FreeSound.org and put them into a new set in Farrago.

First up, I added a bunch of on-demand effects. These are unsettling growls, howls, and cackles which I can play at random. I then added a bubble sound effect, to help sell my cauldron. Finally, I put in the spooky music file I made in the last step with GarageBand. I set the music and bubbles to loop, so they’ll provide he backing track and run continuously.

One great advanced feature of Farrago is MIDI triggering, which I’ll use to avoid the need to carry my 27” iMac to the front door of the apartment. The iMac can instead remain on my desk, running all the audio behind the scenes, while I control it remotely with an iOS MIDI trigger app on my phone.

I’ve set up an app called TouchOSC to control Farrago, though most any MIDI app should work. If you need help getting your iOS device talking to your Mac, this link should help.

Sending to Speakers with Airfoil

Farrago isn’t the only Rogue Amoeba tool I’ll be using. I’m also going to use our home audio streamer Airfoil to wirelessly send the desired audio from my Mac to speakers set up outside my front door.

The two speakers I’m going to use for this are my HomePod and a bluetooth speaker. Airfoil is a big help here, as it can send in sync to both bluetooth and AirPlay.

I plan to set up my speakers around the entrance to my house, and then set them as outputs in Airfoil, with Farrago as the source. Streaming audio using Apple’s AirPlay introduces a slight lag, but it should be plenty speedy enough to get some good jump scares.

In Airfoil, I just select Farrago as my source, and then click the Transmit buttons next to my desired outputs.

Audio is now streaming to my HomePod and Bluetooth speakers – perfect!

Getting It All Together

At this point, I have everything I need for the 31st. When the time comes, I’ll set my custom creepy music and bubbles playing on a loop, and use the MIDI app on my phone to trigger sound effects remotely. The sound coming from multiple sources in sync creates a very cool effect, like the sound is coming from everywhere, and is going to help sell the creepy vibe. A smoke machine, coloured lights, and creepy decorations from my son will bring it all together and make good creepy fun for all the neighbourhood kids.

Happy trick or treating!

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