Making Music
  Computer Music Software and Hardware

Bend it like Beckham

An extension of pitch shifting a sample is pitch bending it. This is a wonderful effect not available in all audio editors but it is in Sound Forge, WaveLab and Adobe Audition, where you can gradually change the pitch of a sample during its production. So you could, for example, increase or decrease the sample pitch as it plays back. But more than that, these three editors let you draw pitch envelopes onto the sample so the pitch can be varied any which way during production.

While we struggle to think of a musical use for this, it can be used creatively for special effects, creating fast or slow pitch changes within a sample. On a more global level it can be used to create the effect of a record (remember them?) slowing down. Use it at the end of a song (of a suitable genre, of course), to slow it down and stop as an alternative to a fade-out or sudden stop ending.

Channel crossing

If you need to convert a stereo file to a mono file or vice versa, you need a Channel Converter function. The stereo to mono conversion ought to be straightforward. Theoretically, all you need do is mix the two channels into one but some editors let you determine how much of each channel goes into the final mix.

Just a phase If you look at a waveform, say a sine wave, in an editor, you'll see half the wave is above the zero line and half is below. If you copy the waveform and move it half a cycle to the right, you'll see that when one is positive, the other is negative. They are the exact opposite of each other and are said to be 180% out of phase. The phase has no effect on the tone and the two signals sound absolutely identical. However, if you sum these signals together they will cancel each other out. In a stereo recording, if the phase of one side of the signal has been inverted some parts of the sound may fade in and out. The Phase Invert function in an editor allows you to correct a stereo signal in which one channel has been inverted. Not something you'll need every day but useful to have in your editing arsenal.

Normally you will want 50% of each but if you're into karaoke (spit!) you can try the trick of converting a stereo to mono recording with a left mix of +100% and a right mix of -100%. Most vocals are mixed smack bang in the middle of the stereo image and this setting will invert the phase (see side panel) before mixing, the idea being that the common signal content - that is, the vocal - will be removed or severely reduced.

Converting mono to stereo is just as easy - you simply copy the recording into both left and right channels of a stereo file. Some editors have a specific function to help with this but it should not be difficult with any editor. However, all you have now are two identical mono channels and not a recording with a sense of stereo placement. But, of course, there are effects to help. Adobe Audition's Echo Chamber, for example, can give a stereo effect to mono material by adding ambience effects. It lets you specify positions for 'left' and right' microphones and by increasing the distance between the Mics, a pseudo stereo effect is produced. Audition also has a Pan/Expand function that can expand (or narrow) the stereo separation of the left and right channels.

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