DUCKING YOUR RESPONSIBILITY
In addition to their more conventional applications, compressors may also be used to enable one signal to control the level of another. This is known as ducking, and is frequently used to allow the level of background music to be controlled by the level of a voice-over. When the voice-over comes in, the level of the background music drops, but whenever there is a pause in the speech, the background music is restored to its former level, at a rate set by the compressor's release control.
To try ducking, you'll need a compressor with a side chain access socket. This allows an external signal to control the compressor action rather than the compressor's input signal. When an external signal is patched in to the side chain, its dynamics will control the gain reduction of whatever signal is passing through the compressor at the time. Let's assume that a piece of background music is being played through the normal compressor input, but that the side chain input is being fed with a voice signal from a mixer send or direct channel output. The diagram in this box shows how this is set up in practice. When the voice exceeds the threshold set by the user, the compressor will apply gain reduction to the music signal, and when the voice pauses, the gain will return to normal at whatever rate is set by the release control.
Ducking is often used in broadcast, to allow DJs to interrupt and spoil perfectly good pieces of music. Exactly how much the music will be turned down depends on both the threshold and ratio settings, and some experimentation will be necessary. The attack time should normally be set fairly fast, but the release time should be long enough to stop the music surging back in too abruptly. A release time of a second or so is a good starting point.
Even though ducking is possible with a compressor as described, it is even easier to achieve using a gate equipped with a dedicated ducking facility, such as the Drawmer DS201. If you have one of these gates, then I suggest you take the easy way out and use it. The technique is not confined to radio voiceovers: it can also be used creatively when mixing music. Perhaps the most useful application is to force backing instruments such as rhythm guitars or pad keyboard parts to drop in level by a dB or two when vocals are present, or when someone is taking a solo. When mixing, a change in level of as little as 1dB can make all the difference between a solo sitting properly in the mix, and either getting swamped or being over-loud.
Ducking can also be used in a similar way to push down the level of effects such as reverb or delay, so that they only come up to their full level during pauses or breaks. This is a useful technique to prevent mixes becoming messy or cluttered.
how do I have to ask my question to get any response?
. but hey - who said mixing was easy?
) it works just as well.