Tuesday, May 27, 2014

Circle of Fifths

The circle of fifths is the first thing that we learned about in Physics of Music. It is something that musicians use to help represent the relationship of the 12 notes of the chromatic scale. It shows how closely the keys are related to each other. The circle of fifths also has a basis in science and the harmonic series, because the interval from the second harmonic to the third harmonic is a fifth as well (A to E).  It uses every single note in the 12-note scale once before coming full-circle. The dodecahedron was a 12 sided 3 dimensional object that we built during the second week of our class. It represents the circle of fifths and how it progresses from each note to the other.

The Harmonic Series

The harmonic series is the sequence of all multiples of a base frequency called the fundamental. During the harmonic series a string or a column of air divides itself endlessly and the frequency gets higher. Frequency and wave lengths are inverses. For example, when the waves length divides itself in half, the frequency multiplies itself by two. Many instruments use the harmonic series either directly or indirectly. A brass instrument uses the harmonic series directly and produces the different harmonics in order.

Frequency of Piano Keys

During the first few weeks of this class we studied frequency. Frequency is the rate at which vibrations occur in waves and are usually measured per second, which are called Hertz. If you have a string with a certain frequency and you cut it in half, the frequency would be multiplied by two and this will continue forever because as the string gets smaller by halves the frequency doubles.These are called octaves. When a string is divided into thirds, it forms a musical interval called a fifth.  A standard modern piano has 88 keys and one way of determining all their frequencies is to use octaves and fifths.  We used this method to calculate the frequencies for every note of the piano. Although this is the simplest method, it has some problems and musicians usually use a different method to tune a piano.  

Different Systems of Tuning

Pythagorean, equal temperament, and just intonation are 3 different systems of tuning. Pythagorean and just both are based on the naturally occurring harmonic series. Equal temperament is a compromise and can be derived mathematically. All produce scales with a different third. Pythagorean tuning uses only perfect fifths, just intonation uses perfect fifths and major thirds while equal temperament uses cents and 12 equal notes to an octave.

A Trip to the Organ

During Week 2, the class went on a trip to the St. Mary’s Church organ. This was a very interesting trip because the organ was big enough that we were able to crawl inside, and examine the vast number of pipes within the organ. We learned that the organ contains hundreds of pipes varying in shape and length. The largest pipe was 16 ft long and had a width that resembled that of a small tree, and the smallest pipe was about the size of a straw. Each pipe releases a completely different sound from one another. There are so many pipes that you need to use knobs (called drawbars or stops) and pedals to be able to access many sounds able to play in the organ’s vast range of musical sounds.   



Building Pipes Whistles


During the second week of class we built pipe whistles with pvc tubing. First, we picked one fundamental note for our whistle. Then we used the equation Velocity = Frequency x Wavelength to find the wavelength and then the pipe length for an open column of air. Then we cut the pvc pipes with the right measurements so they would produce a sound that was close to the note. For the whistle to work well, we had to make a sharp edge to split the air stream. When all of this was done, we tried to match the sound of the piano with the sound of the flutes to see if our calculations were correct. Finally we made more calculations to add the holes in the right place, so it could produce more notes.




Building the Guitar

In the second week we built a guitar. Dr. Fletcher built most of the body and our responsibility was to calculate where the frets would be placed, cut them and glue them in place. Unlike making the Pvc pipe whistles, where the length is fixed, we only had to worry about ratios because guitar strings can be tuned based on tension. We figured out each notes’ location by relating it to a fifth above it or below it. We put two strings on the guitar. Dr. Fletcher also explained to us that the placements of frets is not the only important part to have a well tuned guitar. You must also consider the string type, and how tightly the strings are pulled. We also had to create a box with a hole in it that allowed the vibrations to spread through the box. This amplifies the sound so we can hear it clearly.








Synthesizers and Waveforms

Synthesizers use different waveforms to produce different sounds.  A sine wave produces smooth curves and only has the fundamental frequency present. A sawtooth wave has one side that is an angled ramp up and another side that drop straight down. A sawtooth wave has all harmonics present and it sounds very harsh and piercing.  A triangle wave only has odd harmonics present. An example of an instrument that produces a triangle wave is a clarinet. A square wave also only produces odd harmonics. It looks like a divided line.

Envelopes

Envelopes are a critical factor in sound and the production of synthesized music, and they basically control how a sound is produced. The different parameters of envelopes are known as Attack, Decay, Sustain, and Release (ADSR). Attack controls how slow or fast a note takes to reach its maximum volume. Decay controls how slow or fast it takes a note to level down to its sustain volume. Sustain is just the level at which the notes holds steady, and finally Release handles how slow or fast it takes a note to decline back to zero volume level. These are the main sections of envelopes. They are typically applied to filters, volume or in some cases both.



Filters

Filtering either eliminates or  emphasizes frequencies. It can change the harmonics present, which changes the timbre (tone). One example is a low pass filter. This filter lets everything below a specific frequency to pass through. Another one is a high pass filter. It lets everything above a certain frequency to pass through. Lastly is a notch (band-pass) filter. It blocks out very specific parts. Filters can be modified and affected by envelopes and low frequncy oscillation.



LFOs

LFO’s or Low Frequency Oscillators are a frequency below 20 hz (Human Hearing) that uses a selectable waveform to create a rhythmic sequence in a synthesized sound. In class, during the third week we explored Modular Synthesis and one of the projects was to make a distinct synth sound using one of the aforementioned LFO’s. LFO’s can be used to modify filters, volume, and pitch. The products were very interesting, though sometimes it was difficult to get it working in the beginning.

Monday, May 26, 2014

Final Synth Projects

As a final project, students were asked to create a song using at least three different synthesizer sounds of their own making.  They used a Tyrell N6 software synthesizer plug-in that was available as a free download and worked with any Audio Units host program, such as Garageband.  The sounds needed to demonstrate different waveforms and the application of envelopes, filtering, and low frequency oscillation in a musical setting.  Students had the option of recording vocals as well.  The results are below:

Tucker and Desir

Louis: Boys on the Block

Perez & Vanheyningen

Vincent & Egberongbe

Blount & Stone

Knighton & Ziao: Cypher ($BP)