The crack team of Paul White and Hugh Robjohns have travelled the world solving readers' problems. Here, they down the Hob Nobs and answer some of your recording queries in our Q&A mini-series, Sound Advice.
Paul: The most common brass instruments you'll find recorded in home studios are trumpets, trombones and saxophones (the sax is technically a woodwind instrument, as it has a reed, but is so commonly found in 'brass' or 'horn' sections). Recording brass is something I do relatively infrequently but it has never really presented any serious problems. As long as you make some effort to get the mic where it sounds best, and make the player aware that if they move around, the timbre of the sound will change dramatically due to the extreme directionality of brass instruments, the rest is pretty easy!
Hugh: In the case of trumpets and trombones, the majority of sound comes from and projects in the direction of the instrument's bell. The 'polar pattern' of the instrument becomes increasingly directional with rising frequency. If you stand behind a trumpet you'll hear very little direct sound and no HF components at all. If you move to the side you'll pick up the lowest frequency components, but it is only directly in front that you'll hear the higher frequency components and harmonics (above about 4kHz).
Paul: So for the sharpest, crispest sound you'll need to place a mic directly in front of the bell either on a fixed stand or clipped directly to the instrument itself. If you're concerned about room reflections, then some suspended duvets behind and to either side of the player will help damp things down. As is often the case, if the room doesn't flatter the instrument, then it is better to damp out as much of the room as you can and then replace it with a more sympathetic reverb when you come to mix.
Hugh: You need to bear in mind that brass instruments are designed to be loud. Trumpets have been measured at four metres to produce over 96dB SPL, and around 130dB SPL just 0.5m from the bell. A trombone is roughly 5dB louder still. So microphone choice means finding a microphone that can accommodate huge peak levels without excessive distortion.
Paul: But every cloud has a silver lining, so they say, and the high SPLs of brass instruments mean that even noisy computers in the same room are so far below the levels of a typical brass instrument, to the extent that, unless you have the mic set up right next to the computer, noise isn't going to be a problem. Again, some acoustic treatment may be necessary, though, because while you can drown out background noise, you can't drown out sound reflections — they get louder as the instrument does!
Hugh: When it comes to mic choice, a typical studio approach for pop music would be to use classic large-diaphragm condensers such as the Neumann U87 or AKG C414, operating with pads switched in and placed within half a metre of the bell. In practice, most large-diaphragm mics will work fine provided they can cope with the peak SPLs. Failing that, dynamic mics are always a reliable choice that will cope with the SPLs without trouble. Ribbons are also popular, both for pop and classical brass recordings. The Coles 4038 and AEA R44 are favourites, but you need to place them no closer than a metre and use a pop screen to prevent wind blasts popping the diaphragm.
Paul: Unless you have headphones with very good isolation, you may not be able to hear the effect of mic movement when working 'live', so recording a test section while moving the mic and describing the mic positions into the mic as you do it may work better. Further to what Hugh suggested about choosing a mic that can handle high SPLs, I suggest that you leave adequate headroom at your mic preamp and DAW input, as the quirky waveforms produced by some wind instruments can produce misleading meter readings on some less-sophisticated metering systems.
Hugh: The saxophone needs to be treated a little differently, because it generates sound in the same way as that conventional woodwind instruments do: along the full length of its body. This means that a different miking technique is appropriate: the mic should be placed to 'hear' the whole body of the instrument. However, in pop music, it has long been fashionable to mic tenor and baritone saxes very close to their upturned bells (as in the picture), and this captures a very specific kind of sound. It's not the natural sound of the instrument as heard in the room at a distance, but a bright, raspy sound that everyone recognises and now expects.
Paul: Some final advice: when recording, pay attention to the sound quality. It changes as the instrument (and player) warm up, and as the instrument inevitably fills with spit! It pays to give the player plenty of opportunity to clear the instrument and rest the lips, particularly if the playing involves a lot of stabs and high notes. Brass players can tire quickly — these aren't easy instruments to play — so be realistic in how much recording and overdubbing you can do.