How to make a Reverse Glass Effect

Some sounds are ubiquitous standbys, familiar friends that even define and carry the name of a music genre. Others are rare sounds that catch your ears and surprise you. This tutorial is about one of those effects, it will show you how to make a “reverse glass effect” inspired by a sound from the soundtrack of Halo.

To be specific, the track I’m referring to is “Orbit of Glass” from the Halo 2 Soundtrack.

Step 1: Oscillators

We’ll begin by designing a stabby, high-pitched synth sound. Then we’ll play a pattern, render the audio file with reverb, and reverse it. This will be the result:

Download audio file (10revglass.mp3)

First, Load ZebraCM. This is a freeware synth that comes with Computer Music Magazine.

This is the default patch:

Download audio file (01revglass.mp3)

We’ll turn the volume of the first oscillator off, and change second oscillator’s waveshape to “12″, which is a rich-sounding waveform with a little bit of bite.

For a thicker sound, I’ll change the unison to Quad, and to make it higher, I’ll change the pitch by 36, using the Tune knob.

Download audio file (02revglass.mp3)

Step 2: Filter

Next we’ll work on the filter. ZebraCM’s KeyFollow feature makes the filter’s cutoff change according which key you’re playing, but we don’t want this in this situation. Let’s turn the KeyFollow knob to zero to make the filter cutoff sit permanently in one place. We’ll also change the Filter type to LP Middrive, and adjust the cutoff to 20. We’ll need to turn up the volume of the oscillator as well.

Download audio file (03revglass.mp3)

We want to adjust the sound so that it fades from bright to dim, but not as fast as it does now. We also want to make the sound a bit sharper, so that when it’s reversed it will have that “glassy” sound. We have to think backwards and adjust our parameters so that when played backwards it will start out dim, move quickly to a sharp sound and then fade slightly and abrubtly, much like the sound you get when sharpening knives. By default, the filter cutoff is linked to Envelope 2, and we’ll take advantage of it.

With this in mind, let’s adjust the Attack to 13, Decay 40, Sustain 60, and Release 40. I also recommend reducing this envelope’s Velocity knob, so that our note velocities don’t affect the filter envelope.

Download audio file (04revglass.mp3)

Step 3: Volume Envelope

We’ll shape the volume envelope similarly. Adjust the Attack to 16, Decay 35, Sustain 40, and Release 25. Also, let’s set this envelope’s Velocity knob to 100 to make the velocity-volume relationship stronger.

Download audio file (05revglass.mp3)

Step 4: Pattern

Now we’ll work on the pattern. The next steps we’ll take will change the sound dramatically, and it’s difficult to imagine how a pattern will be transformed by them. The best way to find a pattern that works is trial-and-error. I’ve found that the best patterns that work in this context are ones that move up or down a scale quickly and have a feel of acceleration or deceleration. I’ve also noticed that having a melodic zig-zag in faster parts is easier on the ears in this situation. Here is the pattern I made:

Download audio file (06revglass.mp3)

For those following along, this is at 100bpm. We’ll need to reverse the pattern so that we can bounce the sound with reverb and then later we’ll reverse that audio file to get the note order back to normal. Fortunately FL Studio has a flip tool (keyboard shortcut ALT+Y). Be sure to uncheck “Preserve start times”.

Download audio file (07revglass.mp3)

Step 5: Reverb

A bit of reverb is essential for this effect. It smooths the transition from silence and adds something special when the effect is reversed. Let’s load EpicVerb and start with the default patch. We’ll need quite a bit of the effect, so turn the DRY:WET balance to 50-50. Also increase the Predelay to 50ms, and increase the Time to around 1600 ms.

Download audio file (08revglass.mp3)

Now we can bounce the audio file. I recommend selecting the timeline in a way that gives the reverb effect some time to fade out.

If we bring the resulting file into the project and reverse it, here is the result:

Download audio file (09revglass.mp3)

Step 6: Spot Delay

It has the sound we’re going for, but it has a rather abrupt ending. We can fix this by using a technique called Spot Delay. To do this, we’ll need to link this audio clip to a Mixer channel, and then set up a Delay on a Send track. We’ll want to set the Dry Knob to zero, because we’ve already got the audio file sending to the Master track.

Next, select the audio file’s mixer track, and the send knobs should appear. Adjust the first send knob to hear the Delay effect. This knob allows us to send audio to the delay plugin.

Download audio file (10revglass.mp3)

Right now, the track is sending audio the whole time, but we can use automation to send only the parts we want. In this situation, all we wanted was to make the sound fade smoother, so let’s automate this knob to send only the end of the audio clip to the effect. Let’s also have a little bit of the beginning as well.

Download audio file (11revglass.mp3)

Final Tips

The Spot Delay technique can be useful in many situations. For example, you can send certain words in a sentence to the delay plugin or send only the snares in a complete drum mix, by opening and closing the send knob.

For a stereo effect, set up copies of the synth with slightly different pan settings and have the synths play different parts of the pattern.

To speed up the process of finding good note patterns in Step 4, consider bouncing three patterns at once (any more than that and it can be difficult to remember which is which with all the double reversing going on).

For a “glassier” sound, use very high notes and extreme high-pass filtering. This, plus a lot of delay feedback, was in the Halo sound.

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