Room Mode
A room mode is a frequency that resonates due to reflection from the surfaces in a room. Essentially, if the length between surfaces (or the sum of lengths between surfaces) is a multiple of a particular frequency, then that frequency may be amplified. Room modes can be described by the which walls cause them. An “oblique room mode” is one in which all four walls plus the ceiling and floor are involved. A “tangential room mode” involves reflection from two pairs of parallel surfaces such as all four walls or two opposite walls and the ceiling and floor. They tend to be stronger than oblique room modes. The strongest room modes are “axial room modes”, which involve only two parallel surfaces.
Hard, parallel surfaces will resonate at very narrow frequency bands causing very audible spikes. This is one reason acoustic treatment often involves softer materials and often comes in panels with oddly shaped surfaces. The softer materials absorb some of the vibration, “killing” the sound. The odd surfaces prevent what vibration is reflected from subsequently resonating with other parallel surfaces.
Rock Opera
.A collection of Rock Songs which tell a complete story – similar to a traditional opera but with Rock music. This is different from a musical in which there is also spoken dialog
Impedance
Impedance is the resistance of a circuit to an alternating current of a certain frequency. Impedance is composed of static resistance (as we would measure in a purely DC system), as well as the capacitance and inductance of all the components in a system. The resonant frequency of the Impedance is the frequency at which an AC signal encounters the least resistance. Each component in a system will increase the overall Impedance, but may change the resonant frequency of that Impedance. Many audio components are designed to produce the most desirable sound when loaded with a certain Impedance of a certain frequency.
Conventional pickups, for instance, are designed to operate optimally at high impedance (often around 1 megaohm). So, matching the impedance of you amp/effects to your pickups often results in the most desirable sound. This is called Loading. Any effects that use a Buffer will isolate the impedance on the input and output sides, so impedance matching can help determine the optimal order for your audio equipment chain.
Harmonic Rhythm:
The harmonic rhythm of a piece refers to how often the chords change. Music in which the chords change rarely has a slow harmonic rhythm; music in which the chords change often has a fast harmonic rhythm. Harmonic rhythm can be completely separate from other rhythms and tempos. For example, a section of music with many short, quick notes but only one chord has fast rhythms but a slow harmonic rhythm.
Pitch Pipe:
A pitch pipe is an instrument through which one can blow to hear a note, usually used for tuning. While a common form of a modern pitch pipe is a round disk with 13 holes around the edge, one for each chromatic note plus an octave, they used to be a single cynlinder, or pipe, which a lever which, when adjusted, would change the note played. This is why it is called a pitch pipe. Though technically a musical instrument, pitch pipes are not normally used for performing or playing music. They are less accurate than tuning forks, but in many ways far more convenient.
Sources:
Wikipedia
Sweetwater.com’s Glossary
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