ABSTRACT
An in-depth look at the steps required to produce a CD for an a cappella group. From what microphone and preamplifiers to use, to what steps to take during the editing, mixing, and mastering processes. Finished with a look at pitch detection algorithms and how they work, and a little bit of experimentation with my own algorithm and program.
CD
Figure 1. The AKG C-214
Because a cappella deals exclusively with human voices and noises made my human mouths you will want to pick a microphone that does well with detail and clarity. Condenser microphones do well at capturing sounds accurately and in detail so this will be the best choice when recording vocals. Condenser microphones require phantom power to charge them and record sound, so you have to keep that in mind when picking up a pre-amplifier or audio interface.
Figure 3. Microphone Pop filter
You will want to position the microphone directly in front of the singer’s mouth. Tell them to stand with their mouth about 3-5” away from the microphone. In some instances a position farther from the microphone might be necessary due to the volume the singer is singing at. To get rid of any unwanted plosives due to gusts of air hitting the microphone diaphragm, you will want to place a windscreen or pop-filter between the singer and the microphone. The windscreen or pop-filter should be placed roughly 2” away from the microphone.
PITCH DETECTION ALGORITHM AND PROGRAM
Figure 7. An example of the graph output in MATLAB at the end of the pitch detection program
Now your pks array will only consist of peaks that are over 300, which significantly cuts down the number of peaks returned. Now that you have the important peaks it is time to assign the first peak as the fundamental. The first peak amplitude will be located at pks(1) and the first peak frequency will be located at locs(1). For the purposes of this program, only the first peak frequency is important.
FUTURE WORK
Due to time constraints, I was not able to finish a ll that I was hoping to on this project. There is still some editing to be done on the four songs, and also a bit of mixing. The pitch detection program is almost finished, but I need to figure a way to run the program outside of MATLAB.
CONCLUSION
In this paper, I have explained step-by-step instructions on how to record, mix, and produce an a cappella CD. I have also briefly explained the methods used to create a pitch detection algorithm and program. Major concepts to take away from this paper include the following:
• When recording an a cappella CD, or any CD for that matter, there are three important steps: Recording, Editing/Mixing, and Mastering.
• In the first step, recording, make sure you do not rush into anything without thoroughly thinking about the end goal of the recording. Many choices along the way play a huge role in the final product.
Source: California Polytechnic State University
Author: San Luis Obispo
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