Making Music
  Computer Music Software and Hardware

Seamless looping

Zero-X's Seamless Looper has a host of functions dedicated to finding and creating good loops. It is particularly adept at creating loops with a sustain section such as instrument samples designed to be played by a sampler.

Stretching it

Two related and particularly useful processes for both audio tracks and samples are time stretching and pitch shifting. If you speed up a tape recording you'll hear that the time or duration gets shorter while the pitch gets higher, and if you slow down a tape, the duration increases and pitch gets lower. The two are inexorably linked.

However, with digital editing we can now do one without the other. Changing the duration is particularly useful if you need to make a sample fit into a section of a certain length. The term 'time stretching' may be a little misleading as we can 'time shrink' just as easily.

Different editors offer different ranges of functions. You may be able to change the duration by tempo, by time, or by a percentage. Many have an option to change the pitch along with the time, like a tape recording, which may be more useful for creating effects than for song production.

Possibly the most common requirement when working with audio is to change the duration of a sample. Let's say you have found or created the perfect loop but it's too fast or too slow. No problem - time stretch it to the correct duration. You can also use this function with an audio track if you decide you want to change the tempo of a song after recording. This is not recommended but it can be done.

If you try to stretch (or shrink) a sample by too much the result will sound unnatural although the exact degree of acceptable change will depend on the source material. For small 'corrective' adjustments there should be few problems. However, extreme changes can be used to good purpose to create special effects and to create your own sound samples. Again, you need to be aware that large changes will sound unnatural and will introduce artefacts into the audio which will be particularly noticeable if you slow down the audio. This in itself, of course, can be used as an effect. Severe duration changes applied to vocals, for example, can generate interesting sections of pitched and resonant audio that could be used for tunes. The more experimental musician can time stretch specific sections of a sample rather than the entire file to create even more extreme effects.

Mister shifter

Pitch shifting is the sister of time stretching but no longer are they joined at the hip. One of the most common uses of pitch shifting is, perhaps, more endearingly referred to as pitch correction, and that's to pull recordings of poor singers back into pitch. Perhaps the technicians on Pop Idol and the X Factor couldn't find the button. While small pitch adjustments can be made to vocals with built-in audio editor functions, you have more options and will get better results with a dedicated processor such as AutoTune.

In formant Formants are a collection of harmonics that occur naturally in many sounds such as bells and reed instruments but more especially in vocal sounds. They play a major part in giving the human voice its specific tonal characteristics. If you pitchshift a vocal, the formants are shifted, too, and you lose the distinctive character of the voice. The 'chipmunk' effect is created simply by increasing the pitch of a voice. To maintain vocal characteristics you need to preserve the formants during a pitch change. Processors in many sequencers and editors, and particularly effects designed for processing vocals, have this as an option.

Pitch shifting can be used to fit the pitch of a sample to a recording. This is particularly useful if you have a sampled melodic riff in a different key to the song but, again, beware of shifting a sample too far from its original pitch. You may also come across samples that are out of pitch, perhaps by a few cents, and these can be pulled back into line, too. There may also be drum loops and samples that you think would sound better at another pitch - all good candidates for pitch shifting.

As with time stretching, pitch shifting changes the characteristics of the audio, particularly vocals, and many editors have an option to preserve formants through a pitch change. This can also be used when shifting instrument and drum samples and it's worth experimenting with it to see whether you prefer the tones produced with the 'with' or 'without' formants setting.

And, like time stretching, pitch shifting is a good way to marmalise samples during those days when you turn into a sound sculptor.

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