Recording Live Music Performances
Imagine what it was like to be in the front row of U2's spellbinding "Live-Aid" performance. Or being in the front row to see Luciano Pavrotti at the Royal Albert Hall in 1982. These were great events to experience in person, and if not for the fine art of audio recording, would now be lost to all but the people present then. With the use of proper techniques and equipment , performances can be recorded from the audience with a level of quality that preserves the experience of actually being in the venue. This guide will specify the elements shared by all great audience recordings.
Microphones: Specifications Matter
Audience recordings are in some ways more tricky than those using soundboard feeds. Soundboards are a known and controlled source. Sound delivered to the audience is more varied in nature and challenging to capture with full fidelity. Therefore, microphone quality is critical. Dynamic range must be high enough to accomodate extremes of loud and quiet events. A loud rock concert may have levels as high as 115dB. Frequency response must allow capture of nearly subsonic bass notes and sharp ultrasonic transients. The microphones (and preamplifiers if used) must contribute minimal noise to the audio. Use a good quality microphone and avoid the poorly designed el cheapo mics found at many electronics shops. Go to a musical instrument / studio supplier and find microphones meeting at leas the following specifications:
Transducer Type: Dynamic or Electret Condenser Directional Characteristic: Cardioid (to reject off-axis noise) Frequency Response: 30 to 18,000 hertz Sensitivity: -30dBV 28mV 1Pa (high sensitivity) Self Noise: 4 dbA or less (very low noise) Impedance: 150 to 250 Ohms
Microphone gain setting is important. Set it only high enough for ambient sound to be above any hiss in the electronics. This adjustment should be made in a quiet environment before show time, and then not changed. Too high a gain setting will limit dynamic range of the recording and increase the chances of clipping on loud audio peaks. Another technique to prevent clipping is to expose the mics to very loud sound and set the gain below the clipping threshold. Some mics may have only a high or low sensitivity choice - low will probably be best for all but quet acoustic performers.
Making a recording from the best possible location is essential. The most perfect place is elevated 5 to 15 meters above the audience and directly in front of the stage. That is where the best stereo imaging is possible, and noise from individuals in the audience is several decibels below the music level from performers. This is most true at large rock concerts where the sound is amplified and delivered from large speaker arrays beside or above the stage. Do everything possible to place the microphones far from screaming, whistling, or loudly clapping people.
A less than ideal location will present problems. For example, being too close to the speaker arrays can result in overdriven microphones. Being too far causes the sound to contain excess reverberation and audience noise. If the microphones are too close to the stage and out of the aim point of the speakers, the result is a capture of the performers bantering to each other, plus reverberant music without spatial clarity. So make every attempt to place the microphones where the sound is clean and strong, with minimal noise.
An example of near perfect microphone placement is the 1999 performance of Neil Young during his acoustic tour in North America. Less than perfect? How about a microphone too close to chatty U2 fans during their 1992 Zoo TV tour. Two other examples show that placement on a stand near performers gives a signal advantage in small clubs where the audience is close to the stage.
- If using a preamp or microphone with a gain control, keep the levels as low as practicable to avoid clipping on loud peaks. The event should peak around -3 to -6 dB below 100%.
- Avoid compressors and limiters. The objective is a clear raw audio recording with no enhancement or modification.
- Use at least a 48 kHz sampling rate; that allows recording of sound components up to 24 kHz.
- Record in as high a resolution as possible, for cleaner editing in the future. Select 24 bits or higher.
- Filter all power to the microphones, preamps, interfaces, and recorders. Keep out the power line noise!
- If using battery power, use fresh batteries, and parallel enough of them to provide power throughout the event.
- Mount the microphones or recorder on a strong and vibration resistant support.
- Use windscreens - even light breezes blowing across the microphone can interfere with the music.
- Avoid handling the devices while recording. Adjustments should be made PRIOR to show time.
|Subject||Recording Device||Mic Placement||Levels|
Neil Young: Powderfinger
|Sony TCD-D Digital Audio Tape||Front row center
in a quiet audience
U2: All I Want Is You
|Sony TCD-3 Digital Audio Tape||4th row near stage
too close to chattering fans
Jimy Graham: So Different Blues
|Zoom H2 Digital Recorder||On stage near guitarist
performer foot stomping!
Made In China: Blue Suede Shoes
|Zoom H2 Digital Recorder||On stage near bassist
nearly perfect recording
Portable Digital Recorders
After the sound has been picked up by the microphones and transformed into an electronic signal, it should be handled with care and accurately digitized as soon as possible. In a perfect world, the audio would go directly to a high resolution analog to digital converter, thence to a data storage device. What really happens is the signal must be somewhat amplified to line level, filtered of ultrasonic components, and then fed to the A/D converter. A/D converters can completely mangle an audio signal if the signal is too strong, too weak, or contains spectral components well above the intended audio range. Quality audio recorders handle the filtering and gain requirements very nicely, but you should do some testing before the show to verify that the ADC will get plenty of signal without being overdriven. Many recordists simply reduce the microphone gain by 10 dB and get good results on most equipment. If possible, record at 24 bit resolution.
After being digitized, the audio data should be saved to a storage medium of some kind. Flash memory, digital all audio tape, or optical discs have all been used with good results. Popular all-in-one field recorders such as the Zoom H4 are especially suitable since they have no moving parts, record high resolution audio, and can accomodate high capacity flash memory cards. These handheld devices can record more than two hours of stereo audio to as SD memory card.
More sophisticated options are available if one has enough electrical power and desk space to set up a professional digital audio workstation. A personal computer (with plentiful memory, processor power, and drive space) can be used as a hard disk recorder. Do not simply plug a microphone into a laptop and expect good results! The microphones should be connected to a digital audio interface, and the interface connected to the PC. The PC should run an operating system optimised for audio processing, and include Ardour or other hard disk recording software. See DreamStudio, Ubuntu Studio, or KXStudio for examples of complete operating systems designed for recording and editing multimedia content.
Storing Your Recordings
High resolution digital audio consumes considerable storage space. Expect to use a gigabyte for a typical two hour concert. External hard drives make a good choice for storage, but also consider archiving your raw data on DVD or even a second hard drive in case the first one fails some day. The important point is to save the original raw recording, and use it as a source for editing and producing a finished product for general use. All of the rules regarding safe data storage and back-up apply here.
Editing Your Recordings
Editing is the means by which one produces finished music for broadcast, home, or Ipod listening. Use a quality sound editor or digital audio workstation such as Ardour. The objective is to put in the necessary cuts, fades, equalization, limiting, and amplitude dynamics to make the recording sound great for future listeners. LESS IS MORE when it comes to editing. Most of the critical work is in recording; editing is just a touch-up process! Use as high a resolution mode as possible, such as 32 bits, and then save the data in a lossless audio format such as WAV or FLAC. Never forget that mp3 files are for listening on smartphones or iPods, not for storage or home theater usage.
Once the editing is complete, the audio can be cut into individual tracks or shared as a whole in-interrupted concert. A common technique is to cut the performance into individual songs, without fades, and save in a lossless compressed format. FLAC is ideal for thading and sharing via the internet. Another is to save tracks as mp3 files for loading onto music players. Bear in mind that the actual archive should always be kept in a high resolution lossless format.
Modern technology enables any person to make excellent sounding recordings of events ranging from family sing-alongs, club jam sessions, to full fledged professional performances. The techniques described above cover the main elements of audience recording and form a starting point from which one can capture the true sound and feel of an event for future the future listening enjoyment of all. For further reading, great references are Libre Music Production and Recording.org. Both sites have active participants who know the ins and outs of making great field recordings.
Tags: DIY Live Music Recordings, LiveMusic Recording Tips, Microphones, Audio Recorder, DAW Software, Linux Studio Distro