Recording brass instruments can be a daunting task for an inexperienced engineer - largely because you have probably not had the opportunity to record these more unusual instruments during your studies. A few weeks ago a client brought a trombone and a saxophone that he wanted to record for a project. To record these two instruments is not difficult per se, but require sufficient knowledge of their timbres and how the instruments produce sound. When you know this, the biggest challenge is to place the musician in the correct spot in the room; use your ears to determine the best microphone position for the instrument.
Saxophones are reed instruments, which means that part of the mouthpiece include a reed which vibrates when wind is blown over it. The vibration stimulates that air within the tube which also vibrates - thus creating the particular sound of the instrument. Assuming that the sound only emulates from the bell of the sax and therefore placing a microphone there will cause problems when the project goes to mixing, causing the instrument to sound harsh.
Knowing that the sound is generated by the whole body of the instrument should affect how you place your microphone. You can use a dynamic, condenser or ribbon microphone - depending on what you have available and which tone you want. For our session we used a Shure SM57. Firstly, place the microphone more to the right of the player - approximately halfway up the keys of the instrument, slightly facing the bell. A good starting place is to have the microphone about 50 cm away from the instrument and adjust your microphone position while listening to the player performing through headphones.
Recording Brass Instruments
Brass instruments generate sound when air gets blown with pursed lips into the mouthpiece of the instrument. The sonic character of the instrument is produced from the vibration of the bell of the instrument.
To record brass instruments you can select any dynamic, condenser or ribbon microphone that you have available and you should experiment to hear which microphone gives you the best tone for your project; we again used the Shure SM57 for the project. If you place a microphone in front of the instrument facing it towards the bell, a very bright sound will be captured which is not typically what you want. If you place it too close to the instrument it will pick up all the noises that the instrument and the player make during the performance.
Try placing the microphone approximately 50 cm away from the instrument, slightly above the bell of the instrument, aimed towards the mouthpiece. Listen to the instrument being played through headphones and move the microphone to a better position if required. This might be a little awkward to musicians who are used to play directly into a microphone, but it is your responsibility as engineer to explain to them where to stand and where to aim their instruments.
In both scenarios if you want to capture more of the room, move the microphone further back. If you want to capture more of the instrument you can move it closer to the instrument.