Thursday, August 16, 2012

Sound Effects Editing - Repetitions

I'm in the theatre this week, or rather my young and talented assistant is. I got a text from him late last night that one of the sound effects I had cooked up wasn't working out. The show needed a long series of bells. I had located a bell sample in my library and loaded it into the playback software. (MultiPlay is a terrific utility for triggering sound effects on shows by the way.) I told him if four wasn't enough to just loop the sample.

The problem was two fold. First, we weren't told how much of a bell cue to build. Without knowing exactly what to do I just slapped a cue in there. The second problem was that unlike a lot of percussive sounds, you can't just loop a bell sample. As the note rings out it carries right into the next hit. So when he looped the sample, every fourth hit started out clean.

This next part reveals why sound guys get nicknames like Batman and Gandalf. People don't want to know how you do it, they just want you to work the magic. So here's how the answer to the problem came to me in a dream this morning. (Yes, I solve audio issues in my sleep.)

The solution was to take the second group of hits and slide it back so it overlapped the first group. The DAW is set up to do a cross fade on overlapping regions so the cue turned out smooth with very little work.


You can see where just under the name of the first sample is where it originally ended, and would have started up a new set of four with a clean hit. By sliding the first hit back so it lined up with the start of the fourth hit on the first region the cross fade takes care of that for us. That clean hit is faded all the way down as it starts to play. By the end of the cross fade the new region is playing at full volume. Rinse and repeat for endless samples. (It looks different on the right because that's the sample that's selected and it shows the waveform as its affected by the cross fade. If you look closely you can see the wave form of the sample that's being faded out.)

This isn't just for sound effects though. If you're building songs and use a lot of loops it can be tricky to keep things smooth if your samples have long tones in them. If the material allows you can work a cross fade like this and keep your ethereal loops flowing endlessly.

4 comments:

  1. my favorite application for this technique: create guitar chords with endless sustain. :) i usually create two or three duplicate tracks and crossfade manually.

    ReplyDelete
    Replies
    1. Musically the possibilities are endless. I think something that would help take phrases and loop them like this is to have a little extra at the beginning and end so there's something to overlap.

      Delete
    2. right, there's endless possibilities. One thing that just came to mind while listening to you guys talk about it on the episode: when I wanna double let's say guitar tracks, and I don't wanna play it all again, or I only have one take to mix, what I sometimes do is: duplicate the track, slide one track back so it lines up with the original track, but starts at repetition two. (#1: ABCD, #2: BCDA) That way it's a lot like actually doubling the track, since the playing's ever so slightly different. Make sense? Anyhow, back to the episode. :)

      Delete
    3. I love that solution. That's essentially what I was doing with my bell sounds. I'm sure that guys who edit music all the time are light years ahead of me on this stuff.

      Delete

You're the Scotty to our Kirk