Maybe some of you know that MacOSX ships with a set of default AU audio plugins. If you enable Audio Units in Ableton Live you should see them in the plugin devices browser.
There are multiband compressors, low CPU AUMatrixReverb, AUPeakLimiter and others.
One of the most used, in my work, is the AUHighPass filter. This is a hard cutoff filter – it will filter out anything below a defined frequency threshold.
The usefulness in production is that most of the tracks don’t need to include anything below let’s say 100Hz or so in the final mix. If it’s included, it just adds a lot of low-end rumble that will not enhance the specific track. Rather, it will all add up and cause low end energies that muddy up the final mix.
There are some exceptions. For example, in dance music you want the sub-woofer parts, bass and kicks, have the energy present. And the AUHighPass filter actually will help out, as you then carve out the lower frequencies for well-defined instruments. But for hihats, snares, guitars, synths, voices, all the low-end rumble is not needed.
I should actually make a default template for Logic and Live where this plugin is by default always included. Also, I’ve noticed that I need to put in this plugin across all tracks, otherwise if some have it, it will introduce latencies across the tracks… Thus the latencies are evenly distributed. Or, you could change the latency delay values for individual tracks to get everything back in line, but for me it’s just fastest to include this plugin on all tracks — it does not consume many CPU cycles, anyway.