Now that we’ve explored some creative and logistical issues associated with loops, let’s talk about purely technical problems that may arise. Preparing an audio file to loop smoothly isn’t always a simple task, and there are two issues that may cause consternation in the loop editing process:
• Reverb tail
• Zero crossing point
Let’s tackle these issues one at a time.
Reverb Tail
As we’ve discussed previously, a linear loop must end the same way it begins. On a technical level, this means that the audio content in the final split second of the loop should perfectly match the audio content in the beginning split second of the loop. We want these matching bookends because they compensate for the loop’s “tail,” which is
the time it takes for the last sonic event of the loop to fade away to silence. Sometimes this is called a decay envelope because the concept focuses on how a sound decays over time, or it may also be called a reverb tail because the reverberation in the original recording (or any artificial reverb we may have subsequently applied) will usually be the last thing we hear when the final note ends.
Figure 10.10
A waveform showing the decay of a sound, commonly called its reverb tail.
The reverb tail is a sticky issue in loop editing. Simply chopping off the reverb tail at the loop point usually isn’t a good solution. As human beings, we’re remarkably sensitive to fine details in audio content, and even in a very busy musical passage, we may still sense the subtle artificiality that would occur when the reverb we’ve come to expect is momentarily absent at the loop point. It is always better to let the reverb ring out naturally. When we trim the ending of our loop (in our preferred multi-track audio software), we should copy the reverb tail at the end and paste it into a new audio channel at the beginning of the loop so that the reverb tail can play at the start of the piece. This allows the reverb tail from the ending to overlap with the beginning so that we never
sense any sudden absence of reverb.
Now we come to the reason why we want to bookend a looping track with identical note pitches and instrumentation: if the last note of the loop does not match the first, then the overlapping reverb tail will create a sense of inexplicable dissonance and incongruity when the loop first begins. We normally don’t notice the sorts of momentary dissonances created by reverb because our minds can identify the source that created the reverb tail and this allows us to mentally sort things out. When playing a loop for the first time with a dissonant reverb tail overlapping the beginning note, we can’t identify what produced that reverberation and we perceive the result as very unpleasant.
Ensuring that the notes at the beginning and end of a loop are identical in pitch and instrumentation can solve this problem, but doing this can pose a few tricky issues.
Returning to nursery rhymes as convenient examples, let’s use the simple melody from
“Frère Jacques” (“Are you sleeping, Brother John?”) to illustrate the point. We can easily hear that the first “Frère Jacques” ends on the same note on which the second
“Frère Jacques” begins. If the loop ends after the first “Frère Jacques” and then begins with the second, the loop point will be bookended by two identical notes.
Figure 10.11
A simple loop based on the “Frére Jacques” melody.
Depending on how much reverb has been applied, this may enable us to create a smoothly edited loop point. I mention the degree of reverb because in our hypothetical
“Frère Jacques” loop, the amount of reverberation may create problems. If the recording is relatively dry or the size of the room relatively small, then we can be reasonably confident that our “Frère Jacques” loop will work perfectly. However, if the reverb is more pronounced, we may find the reverb tail of the second-to-last note of the “Frère Jacques” phrase bleeding over into the beginning of the loop. In this case, that note is the major third above the root. This reverb tail would give the momentary impression that the first note of the loop is in fact a two-note chord comprised of the root and the major third. We’ll need to make adjustments to prevent this sort of unintended overlap from occurring. These adjustments can be made either during composition or in the editing stage but it is always preferable to think of these issues as early in the process as possible, since this planning tends to reflect well in the final results.
Zero Crossing Point
Those of us who have already edited short audio loops for use as building blocks in our musical compositions will be thoroughly familiar with the zero crossing point, but for the
rest, a brief mention is in order.
We all know that when working with an audio file in our preferred multi-track software, we have the ability to view the audio data as a waveform. We can zoom in on this waveform until its blotchy, jagged horizontal shape transforms into a single line zipping up and down along a path from left to right. As it leaps up and down, the line frequently crosses the precise center of the waveform, which is the zero decibel point on the horizontal axis, also known as its zero crossing point. If the audio in question is in stereo, then we will see two waveforms running parallel to each other, each zipping back and forth over their individual zero crossing points. Their routes over the zero crossing point will rarely be uniformly symmetrical.
Figure 10.12
A stereo waveform illustrating the zero crossing point.
In order to create a beautifully seamless linear loop, the audio edits should occur when the waveforms are both passing simultaneously over their zero crossing points.
Sometimes it can be very difficult to locate an instance where both the left and right channels are precisely situated on the zero crossing point at the exact same time, in which case we may need to settle for “close enough.” To correct for this, we can create tiny fade-outs at both the beginning and ending of the loop in order to force the
waveforms to cross the zero point. The fades should be only a few samples in duration.
We may need to embark on a bit of trial-and-error before we are able to make the loop point perfectly seamless. There are also dedicated audio editor applications that feature special loop-crossfading capabilities (which can come in handy when we are struggling with a particularly difficult loop point). Generally speaking, a rhythmic track will usually be easier to loop. The definitive downbeats of a track with heavy rhythm afford us loop points that are generally easier and quicker to edit. In contrast, ambient tracks with lots of floaty, elongated elements can sometimes be difficult to seamlessly loop. When I resort to using my own supplementary audio editor for the creation of loop crossfades, I usually do so for particularly pesky ambient tracks.
Final Thoughts about Linear Loops
Poorly composed, poorly structured loops can be immensely irritating. For instance, a short track that loops many times and repeats several obvious musical landmarks before it is interrupted is an example of a worst-case scenario when it comes to video game loops. Ideally, most linear loops should be lengthy musical compositions. They should be composed carefully, avoiding the inclusion of landmarks that may unnecessarily alert the listener to repetitions. Finally, no musical track in a video game should be overused, whether that track is written as a linear loop or not. The best video game scores feature many tracks of a substantial length that are composed to enhance the player’s experience within the game.
Video games tend to offer gameplay experiences that last many hours, and developers are constantly striving to offer original content throughout the entire length of their games so that they will remain consistently entertaining from beginning to end. Music should be considered in the same light; therefore, more music is always better than less.
More music in a video game serves to keep a player engaged via the continual introduction of novel and affecting compositions. More music tracks may also ensure that the music is more responsive to the state of the game at any given time by providing the developer with ample options when choosing which tracks should be triggered under which circumstances. When looking at the proposed music budget, the first priority of the development team should be to ensure that there is enough music to provide a satisfying experience for the player. In doing so, the developer can potentially avoid whatever listener fatigue may occur from the excessive repetition of any single musical work.