When I began work on what would become Elliott Smith's New Moon album in 2006, I knew I might have a few noise issues to tackle. One song in particular, "Angel in the Snow," had been recorded onto 1/2'' analog tape at a very low level. The song was beautiful, but the tape hiss was not. I rented a single-ended noise-reduction plug-in from a certain DAW manufacturer, and while it did reduce the sea of tape hiss, I heard fluttery artifacts in the background. Not much later, I stumbled across iZotope's booth at an AES show, and after explaining my issues, I was given access to the initial version of RX Advanced. When "Angel in the Snow" required a new instrumental mix for the film Up in the Air, I used RX on the original transfers of the tape tracks and was blown away at how much better the mix sounded, enough that I snuck a new mix onto An Introduction to Elliott Smith in 2010. As mastering engineer Roger Seibel said, "If it sounds better, use it." Since then, iZotope RX has become one of my most-used plug-ins, and in lieu of writing up the giant list of its features (many I've never even tried yet), I am going to explain how I use RX, and now RX 3, in the recording studio as a tracking and mixing tool.
RX 3 might be perceived as an audio restoration, forensics, and post production tool - and it certainly is - but I mostly use it on recording and mixing sessions. It can be run as a standalone application or a plug-in (AAX, RTAS/AudioSuite, VST/VST3, Audio Units). I use these techniques during tracking to eliminate sounds I didn't want to capture, and RX 3 really helps during mixing, especially on sessions I didn't track myself. In fact, by the end of a session, most of my clients will come to recognize the spectrogram window when I open it, as they've seen it in use repeatedly. Some even go on to buy their own copy of RX after they see what can be done! One thing I should note is that the learning curve is quick. Many of the initial presets will work just fine, and settings are obvious, though this app can go very deep if needed.
Vocals: I'll remove popped P's, mouth clicks, background noises, and bumped mic stands with Spectral Repair's Attenuate or Partials+Noise functions. Even weird mouth sounds, like the ones that appear after L sounds, can be removed from within a sung note for clarity. Harsh S or T sounds can be attenuated by slightly reducing the overall volume or selecting certain dominant components (but watch out, they will sound weird if you are not careful). With cheap condenser mics, you can even tame some of the more offensive transient artifacts and harshness as well. I've used Spectral Repair or Denoise to also remove AC hum and computer-induced hash. Whether Denoise'ing unwanted sounds from whole vocal takes or cleaning up massive tape or preamp hiss, RX 3 does an amazing job of not leaving fluttery FFT artifacts or dulling the highs. One new feature in RX 3 Advanced is Dereverb. It's a bit dangerous, and I found it easy to mangle a vocal track without pushing the settings too far, but when I needed it on a rap vocal printed with too much cheap reverb, I was able to reduce it enough to work in the mix quite well. Another nice, new tool!
Electric guitar: I'll remove amp or single-coil hum with Denoise, oftentimes just on the intro or fade-out of a song. I'll look for and attenuate clicks from stompboxes, scrapes between chords, palm muting noises, and any extraneous sounds with Spectral Repair. Distorted solos can really benefit from a little cleaning up, and this can allow you to make them louder in the mix. If you have recorded a guitar with too much attack or pick sounds, you can apply Declick to soften this up.
Electric bass: I'll remove any hum from DI/amp ground loops, cranky amplifiers, or single-coil pickups with Denoise. Declick is handy for removing pick noise from a bass take if it's got annoying high-end clicks. If I hear weird, honking notes or sounds from the bass, I'll attenuate the sound/note itself with Spectral Repair. Think of it as highly-selective multiband attenuation.
Hammond organ: We have an old Leslie 900 cabinet, and I've tried for years to reduce its built-in AC hum, without success. Denoise allows you to sample the buzz (always record extra time at the head or tail of a song) and remove the hum. If a note pops out in the wrong way due to harmonics (those pesky drawbars!) during a part, I can go in and attenuate the harmonics in Spectral Repair. If someone forgets to put up pop filters, you can also clean up subsonic plosives from the rotating horns.
Acoustic instruments: Once again, think of all the little sounds that you don't want to hear during an acoustic instrument take (guitar, cello, mandolin, violin, etc.). String squeaks, pick noises, fret buzz, strap creaks, breathing, bow scrapes, page turns, and any other distraction can disappear with Spectral Repair. If multiple instruments were recorded together, bad bleed can be removed to some degree as well. Look for boomy, off-axis notes that muddy up the instrument you were mic'ing, and attenuate.
Drums: How about that noise when the drummer switches on/off a snare in the middle of a song? Gone with Spectral Repair's attenuation. That one clicky kick hit on the first downbeat? Remove the high-end transient component, and it fits back in the mix. Did you compress your room mics so much that there's background hiss? Denoise instead of rolling off all the highs. Did the drummer manage to hit a mic? You can remove the worst artifacts of that with Spectral Repair. Want a softer sound in the ride cymbal? Run Declick, and all the sharp, high transients disappear. Oh yeah, did you get a perfect take but some goofball started talking on the cymbal fade-out at the end? You can pull this chatter right out with Spectral Repair. I find myself constantly doing the same for removing audible stompbox clicks (you know, those silver switches) from overhead and room mics when I have a whole band track together in the same room.
Analog effects: Plate reverbs usually have some hum and hiss in the background, and even though my EMT 140 has some amazing custom Hamptone electronics inside, it still suffers from a bit of noise. Single-ended Denoise wipes that out. Denoise also cleans up my tape and analog delay units when I print them back into Pro Tools sessions.
Other uses: Declip will actually work wonders on audible digital overloads. I've been sent a number of mixes with bad overloads, and though Declip won't always completely restore the original tonality, it will help reduce artifacts and harshness. Spectral Repair's Replace function has to be used carefully, but I've fixed gaps in bass notes from dropouts and other damaged tracks like that. When it works on the material at hand, it's kind of amazing. Like, this shouldn't be possible. Another use I have for Spectral Repair is for fixing final mixes before mastering. You know, like those times you miss an odd little high-end click on a fade or something buried in the mix that's annoying. You can get in there and save your mastering engineer some grief.
Although the regular version of RX 3 would keep me happy because it contains the majority of the applications I use most, there are features in Advanced that I haven't yet even dug into but look to be handy. Deconstruct will break a sound into noise and tonal components, and could be helpful with reed instruments, bass, and such. Insight is their metering suite, and I need to play with that more. Dialog Denoiser is intended for post production, but I'm wondering if backing vocals might do well with this. Center Channel extraction (the ol' mid- side trick) is another feature I need to mess with. I'm imagining the uses right now...
These techniques are just the tip of the iceberg of what RX 3 can do, and given that iZotope offers an unrestricted 10-day trial (for the plug-in only), I see no reason not to check this amazing product out. Visit the website for a full list of features and comparisons between the standard and Advanced versions. RX 3 is a massive tool, and if you work with digital audio on a regular basis, you need this application. I can't work without it anymore! (RX 3 $299 street; Advanced $1099; www.izotope.com)