When recording acoustic drum tracks, virtually everyone mikes the snare drum from above to capture the sound of stick hits. But if a bottom mic isn’t also used to record the sound of the rattling snare wires, the drum can sound almost like a bongo at mixdown. You can add sizzle by triggering drum samples or gated white noise, but there is another way: Use frequency shifters and delay lines to add a virtual bottom mic to the mix.
Unfiltered Audio’s Fault Stereo Spectral Shifter plug-in gets the job done in just a couple minutes. Follow along with Fig. 1 as I describe the control settings.
|Fig. 1. Fault’s dual
and delay lines add
a virtual bottom mic
to a snare track for
DOWN TO THE WIRE
The basic idea is to generate a discordant cluster of high frequencies—sounding like rattling snare wires—from the snare drum track. First, put Fault’s Frequency Shifters into Ring (ring modulator) Mode and activate the Anti-Alias button to filter out generated frequencies that are above Nyquist (half that of the sampling rate).
Crank Fault’s Frequency Shifter knob fully clockwise and raise the Mult (frequency multiplier) control to roughly between x1.5 and x2.2; these settings will generate frequencies roughly 1 kHz higher than the snare drum’s dry sound. Set the Spread control to roughly x0.9 to lower the frequency of the right-channel shifter slightly with respect to that of the left-channel one. In Fault, both the left-and right-channel frequency shifters contribute to processing a mono signal; set the Pan control to the noon position to give them equal weight.
Next, boost the frequency shifters’ left-and right-channel Feedback knobs (in the Feedback Matrix) to between 1 and 1:30 o’clock positions to make the processed sound sizzle more. (Caution: higher settings could produce runaway oscillation.) These knobs shift the generated high frequencies again by the same interval, adding yet more frequencies at the plug-in’s output; unlike with delay feedback, shifter feedback happens instantaneously, and the result sounds like a timbral shift higher rather than a series of discrete tones rising. You can also raise the shifters’ X (cross-channel feedback) control very slightly to thicken the resulting burst of noise; if the sound starts to break up, lower the control.
Next, we’re going to slightly increase the duration of the burst of noise generated by the frequency shifters. Dial in roughly 5 and 5.5ms Delay settings respectively for left and right channels, and set all three Delay Feedback controls (Left, Right, and X, in the Feedback Matrix) to roughly 12:15 to 12:30 o’clock. (Again, higher settings could produce runaway oscillation.) Adding delay feedback sends the entire processed signal (including the frequency shifters’ wet signal) back for processing again, creating an extremely dense cluster of harmonically unrelated, high-frequency noise. It’s important to note that Fault’s delays are feedback-only effects—they do nothing unless their feedback controls are turned up. This construct allows the frequency shifters’ wet signal also to pass through to output undelayed, making the noise cluster even denser—and very briefly sustained—when combined with delayed signals.
BOOST AND FILTER
If you’re not hearing enough “bottom mic” at this point, turn up Fault’s Input (gain) control roughly 5 dB to prolong and intensify the feedback effects, augmenting the number of virtual snare wires rattling. In Fault, cranking the input gain doesn’t affect the dry signal; it only gives you more effect.
If the sound is too bright or brittle, lower the Feedback Filter’s LP (lowpass filter) control to roughly the 1 o’clock position to roll off some highs. (Make sure the Filter All button is deactivated to avoid also dulling the dry signal.) Finally, set Fault’s Dry/Wet knob to between roughly the 10 and 1 o’clock positions to add the right balance of “bottom mic” to the snare track’s top-miked sound. With the right settings, nobody will ever guess your bottom mic was a plug-in!
Michael Cooper is a recording, mix, mastering, and post-production engineer and a contributing editor for Mix magazine. You can reach Michael at firstname.lastname@example.org and hear some of his mixes at soundcloud.com/michael-cooper-recording