In 2017, the Youth Symphonic Band of Colombia presents its concert series “Celebra la Música”, an orchestra made up of 98 young musicians from different regions of the country, this time under the baton of the Italian director Remo Ceccato, with the collaboration of local talents for the interpretation of “Llanera music” works included in the repertoire. This special concert stands out for its location, 120 meters underground in a labyrinth filled with passages that seem to have no end, there are several rooms, auditoriums, and spaces dedicated to tourism and the history of a salt mine located in a mountainous formation (A almost 50 kilometers from Bogotá in Zipaquirá) which origins date back to the birth of the Andes mountains around 250 million years ago, and whose mineral has been exploited since the pre-Columbian period by the Muisca communities that inhabited the region.
One of the most relevant constructions of this old salt mine is its main cathedral, initially built as a congregation center for local workers in the 50s and re-designed in the 90s to captivate the general public with its magnificence and history. This cathedral has an area of approximately 800 meters and an average height of 22 meters, providing a volume larger than 16,000 cubic meters; This added to the reflective surfaces that delimit the place provides an exotic, extravagant, and perhaps illusory acoustic behavior. You only have to clap your hands once to be amazed by the way the sound travels not only through the cathedral but through all the tunnels, mining chambers, and auditoriums of this immense salt mine. After 5 seconds it becomes clear that it is not necessary to continue paying attention to the way the sound travels through the place as it merges with the murmur of the people who walk through the passages and attractions arranged throughout the mine, the challenge of a colossal symphonic recording with 100 performers is accepted with a bit of nervousness and expectations as huge as the cathedral itself.
Image 1. General view of the Salt Cathedral of Zipaquirá
The repertoire includes music from all over the world, composers such as John Williams, H. Owen Reed, Ferrer Ferrán, among others make up the varied sample of this ensemble. The biggest challenge appears at the moment in which several Colombian pieces are performed at the end of the event, works that have a marked percussion and short transients that belong more to local folklore than to the usual orchestral repertoire. Reverb and early reflections management represent a challenge when implementing capture and mixing techniques to achieve a compact sound without relevant delays and phase problems.
Image 2. Internal map of the mine.
The orchestra
This wind/percussion ensemble of almost 100 musicians is made up of a wood section in which you can find more than 20 soprano clarinets, 2 bass clarinets, an arrangement of 10 flutes plus 2 piccolos, 4 oboes, an English horn, and soprano saxophone, 4 alto saxophones, 2 tenors and 2 baritones. 4 Fagots complement the woods, 8 French horns, 8 trumpets, 6 trombones, Euphonium, 4 tubas, and a robust section composed of 4 double basses. The percussion has about 8 players and a wide variety of instruments.
Image 3. Symphonic Youth Band of Colombia
The logistical inconveniences, the inability to hang microphones, and the irregular terrain have led us to opt for a low location for the main microphone array, which is not at all negative considering the long reverberation time characteristic of this location. We want to place the microphones in the direct field, considerably close to the orchestra compared to other recordings in concert halls. The colossal volume of this location will be in charge of providing the recording with a strong level of reverb, an aspect of the audio that will not be necessary to support in the mix with any kind of plug-in or spatial design.
The Recording
For the Main, the AKG P420s have been crucial in getting a close capture of the ensemble and a practical level of cathedral reverb. Another stereo arrangement has been arranged in the center of the woods to support clarinets and oboes, the latter ones often requiring assistance in terms of gain. Then we have two microphones intended as an arrangement that seeks to capture the saxophones and clarinets behind the wood section on the left side of the image above (made with a pair of Behringer C4s). Continuing with a wide array of dynamic microphones for the percussion section, two Shure microphones are positioned in the center of the percussion group and the other two dynamic microphones seek to capture the marimbas and the glockenspiel. A crucial microphone is the harp “spot”, a key instrument in the interpretation of some of the works of the repertoire, as well as the implementation of the AKG D11 for a close capture of the double basses, supporting the lower frequencies of this instrument. 12 microphones of which only 3 have required restoration treatment due to power-related noise issues and probably the numerous light connections that were necessary for this naturally dark space.
The Mix
Most of the microphones described above have been gathered in order to give them group treatment, the main stereo arrangement has been edited directly into the auxiliary channel where both microphones have been sent. Waves NLS has been used to give a slight distortion to the signal, and excitation stages have been implemented in order to enhance the high frequencies in a freer way, compared to situations where bowed string instruments are right in front of the Main arrangement. The iZotope imager has been used to open up the stereo image a bit in the high and low frequencies, emphasizing the way they rumble crosses the cathedral. The arrangement has also been treated with Mid-Side EQ to make slight corrections in the low-mid range.
Image 4. Treatment of the main microphone array.
The pair of dynamic microphones supporting the marimbas and glockenspiel located on the left side of the ensemble (director’s perspective) have been treated as a small stereophonic arrangement where only the outer microphone has been panned slightly to the left. The NLS has also been used here to add mild harmonic excitation to the signal. IZotope’s Harmonic Exciter Tape algorithm has been used in conjunction with an equalizer to bring out important high frequencies, giving clarity to the attacks of these instruments that generally stand out melodically in this range of the spectrum. This pair of microphones have not been sent to any bus or auxiliary channel.
Image 4. Treatment of the main microphone array.
The pair of dynamic microphones supporting the marimbas and glockenspiel located on the left side of the ensemble (director’s perspective) have been treated as a small stereophonic arrangement where only the outer microphone has been panned slightly to the left. The NLS has also been used here to add mild harmonic excitation to the signal. IZotope’s Harmonic Exciter Tape algorithm has been used in conjunction with an equalizer to bring out important high frequencies, giving clarity to the attacks of these instruments that generally stand out melodically in this range of the spectrum. This pair of microphones have not been sent to any bus or auxiliary channel.
Image 5. Treatment of the microphones of the Marimbas and the Glockenspiel.
The arrangement for the central percussion has been panned slightly to each side and sent to an auxiliary channel for processing. However, each microphone was treated individually to enhance the characteristics of the instruments involved (tympani, minor percussion, cymbals). It is worth mentioning the use of “Envelope shapers” to enhance the attack of these instruments and obtain a clearer direct signal with greater amplitude in their strong attack transients, this added to the correction of distance referred to the Main (in this case done manually by moving the tracks with respect to their original position regarding the Main), provides us with a more concise signal of these instruments and avoids that the acoustic properties of the place affect the intelligibility of these drums, cymbals, and dry hits. Although it is not possible to correct one hundred percent of these delays and “slap-delays” given by the early reflections and their different arrival times, clearer percussion is obtained in comparison to non-edited percussion tracks, especially for the more folkloric works.
Image 6. Treatment of the percussion microphones.
The microphones that support the rear section of clarinets, the flutes, and saxophones have been treated with Waves’ Z-noise. this is because the microphone on the left (Clarinet section) had continuous noise issues. Although both microphones were routed to an auxiliary channel, their panning is based on their physical location and has not been addressed as a stereo arrangement.
Image 7. Treatment of clarinet, Flute, and Saxophone microphones.
The microphone array located in the center to capture the instruments located at the front of the ensemble has required treatment on its right microphone due to certain continuous noise problems presented during recording. These microphones have also been treated with iZotope’s Harmonic Exciter to give each section its individual frequency treatment. Panning has been treated in the same way as the previous arrangement.
Image 8. Panning and treatment of the center microphones.
The double bass section has been supported by Waves RBas which helps us to boost frequencies below 100 Hz. This range has also been supported by the exciter and a slight equalization, not to mention the use of the NLS to add some distortion and slightly exalt the instrument’s attacks when played with a bow. Band compression has been applied with the Waves C6 to control the resonances (around 130 Hz) that can appear in the loudest passages of the music.
Image 9. Bass microphone treatment.
Regarding the Harp, the microphone has been treated with the Z-Noise and a subtle harmonic distortion has been added with the Tape algorithm of the iZotope Harmonic Exciter. The channel is slightly offset to the left and features a remarkable equalization to enhance the high frequencies of the instrument. This has been the only channel treated with a long decay reverb implemented with the help of Valhalla’s Vintage Verb. This has been done in order to add and mix the instrument with the sound of the main microphone arrangement since in it, the harp is not perceived at all and the spot located for its capture is the only way to highlight this instrument. By getting a relatively dry sound coming from a cardioid microphone very close to the source, the reverb of the orchestra masks any possibility of having a naturally reverberating harp sound.
Image 10. General treatment of the Harp.
Image 11. Harp microphone reverberation.
The auxiliary channel of the percussion has two phases of slight compression to control the most prominent level peaks of the recording. In addition, a subtle harmonic excitation has been applied with the Klanghelm SDRR.
Image 12. Treatment of the auxiliary percussion channel.
The clarinet, flute, and saxophone arrangements have been treated with mild harmonic excitation in the high frequencies and a subtle EQ module.
Image 13. Treatment of the auxiliary channel of Clarinets and Saxophones.
Harmonic excitation processes have been applied to this mix with Waves’ NLS Buss mode, a band compression to control the mid-low range where considerable resonances can occur in loud and tutti passages. Slight alteration of the high frequencies with the iZotope imager as well as a subtle harmonic excitation mixed with minor corrections in frequencies made with the Pro-Q2 and the Waves H-EQ in their Mid-Side mode. At the end of the chain, the FabFilter limiter with its “transparent” mode has been crucial to control the dynamics in the final stage.
Image 14. General treatment of the final stage.
Image 15. Limiter configuration at the end of the chain.
This dynamic treatment, so important in the genre, must be accompanied by careful attention to the volume of each track and stereo arrangement if you want to take advantage of the gain obtained in the recording. The automation of the output level of these channels must be done with great care and attention to the dynamic changes in the different pieces that make up the concert repertoire. An overview of these gain automation across various pieces and tracks has been added below.
Image 16. View of some of the automation made in each microphone of the recording.
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