Audio Recording Issues – Overtones That Overstay Their Welcome, Part OneNext on the list of EQ ideas is solving a rather unusual set of circumstances. Overtones are sounds that occur from various sources that are recorded in addition to the main source sound. Vocals, guitars, drums, and any instrument that is being miked live in a room can be the center of attention for this situation. Overtones can come from room reflections and ambience, from the instrument itself, and they can also come from the addition of effects at a later time, or speakers amplifying a keyboard or guitar amp. There are overtones that come from the musical response of the instrument itself. They can either work with or against the primary sound being recorded. A microphone and a preamp can add creative harmonic overtones to sound material as well. These are mostly natural responses and elements to sound ambience, resonance, vibration, string sustain, speaker cone response, and natural instrument character.
Sometimes these are beneficial and are desired elements in your recording. Other times, we might think we got a great take, but when we go to mix, we realize things are not sounding quite right. Often what happens is that an instrument resonates in a beautiful way or a room gives a great sustain, deepening a performance, or adding liveliness and power to a drum set. But, when these instruments are added together, we discover that some of the beautiful overtones are coming across as actual conflicting notes. They may complement the individual instrument performance wonderfully, but the interaction of multiple instruments recorded with their own microphones may be in conflict.
It may be that the perception that the supporting sound architecture works until it overlaps with other tracks. There is a perceived crossover of smooth, long waveforms that now conflict with others at multiple Frequencies. We don't notice the distraction until they bounce off of other sounds. We may get short bursts of shorter waves that oscillate and accentuate the fact that both conflicting waves are off pitch from each other.
In the same manner that a good chorus effect detunes an accurate pitch slightly above and below the natural pitch, overtones can conflict by forcing your brain and ear to pick up on distortion between tones that are off from each other and the original instrument. You can get very dissonant short fast waveforms from two overlapping, otherwise pleasant, overtones. Harmonics usually structure themselves intentionally and nicely above a root fundamental, but ambient overtones can clash in an endless assortment of situations.
In other instances, overtones start as a nice balance with the instrument, but as the sustain of the root note kicks in, we hear more of the overtone or room ambience and this resonance now interferes with the tonal character of another track. Sometimes this works to our advantage and other times it causes serious balance issues.
A classic example of overtone issues comes from the decision making in recording a live drumset. First, a great sounding drumset requires a knowledge of how to properly tune the drum heads. You have various pitch options, and when you make this decision, you need a balance between the top and bottom heads. Then, you need a knowledge of how to tune each drum from the next. What is the pitch difference between drums supposed to be? How many full notes or half steps sound best from the hi tom, mid tom, to floor tom? These decisions also pertain to the song being recorded. If you have an extremely tonal drumset, you don't want to spend hours tuning each head just right, only to find out that you are micro-tones off from the perfect tuning of the song, and now every sustain of that awesome drum is going to sound like a terrible pitch in the song. Anything that can be done to correct pitch before recording your tracks can offset the number of concerns come time to mix and master.
Let's pretend that you paid attention to these details. Your drums sound awesome with the songs and other instruments. The room is really grabbing this great energy from the set. Now, when you pull up the room mic's or overheads, there is a strange clash going on. What happened? Assuming there is not a phase, distance or timing issue from the multiple miking setup, you can have a variation of surface responses to pitch, reflection time, and so many variables between the attack of direct microphones and distant room microphones.
All of these issues come up in real world scenarios and must be dealt with in the best possible ways. If gobos or various room positions are available, you may get the perfect control over the room just from walking around the room and listening to takes before your final recording. If there is simply too much going on to spend all day working out the ambient kinks, then EQ may be the best response. This is especially true in the fast-paced world or recording, where every second of the session matters, and it is equally true when artists have a window of time for their best performances and creative ideas.