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.