Chordophones Physics of Music PHY103 from ANIMUSIC by Wayne Lytle

Tradeoffs in chordophones Strings only High tension means a lot of stress on the instrument. More massive strings have lower pitches under lower tension However thick strings don’t bend very easily –L oss of high frequencies leading to dull or soft timbre. –Shift of overtones sharpwards

Piano spectrum 347Hz 697Hz 1396Hz 1094Hz Higher harmonics are higher than multiples of fundamental Why? Wave equation requires more energy for shorter waves – non-linear wave equation on string 347*2= *3= *4=1399

Are these frequency shifts important? Butler(example 2.4). a) Piano playing C4 b) Piano playing C4 but the partials have been lowered by digital processing so that their frequencies are exact integer multiples of the fundamental. Pair of tones repeated 3 times.

Bass strings If you lower the tension too much the tension changes during plucking or hammering. The pitch changes after the pluck. The strings flop around leading to buzzing and fast damping.  Low notes then requires thick and heavy strings (metal ones) to prevent these problems. Wound strings help reduce problem of loss of high frequencies. Problems with wound strings: damage to fret-board and fingers particularly for fretless basses. To keep corrosion from reducing high frequency response  plastic covering. However stretching of plastic may damp string motion faster. If the tension is too low then the string will hit the finger board. This is less of a problem for a harp but is a big problem for a guitar or lute.

Soprano strings Require light strings and high tension (for a given tension). Metallic strings are tiny and kill your fingers. Many steel string lutes/guitars are not plucked by hand. Gut or nylon strings are softer but damp faster and are less bright.

Tradeoffs in the strings Length/tension/density – ease of play, position of plucking, having strings of different notes on the same keyboard or fret-board, strength of instrument. String composition – metallic – less damping but heavier, harsher and more damaging to fingers and fret-boards – Gut or nylon – softer/duller but lighter and damping faster

Amplification: A string by itself is not a very good radiator – it has a small surface area. To increase volume the vibration must be coupled to something with a larger surface area. Box: guitar/zither - vibration passes through bridge– faces of the box vibrate. The surfaces of the box vibrate in modes as does the air inside.

Amplification (continued) Box with holes – air moves in and out (violin, guitar) Box with a membrane (African lutes) vibrations excited in the membrane too. The string excites harmonics, some are amplified more than others depending on the coupling of the string to box and the way the box resonantes.

Examples of Chordophones Box Zither- Santoor India Box zither – trapezoid box with many parallel strings, strings are struck Santoor (Indian) Music taken from CD Musical instruments of the World 1990 CNRS

Vietnamese Board Zither 16 steel strings above an oblong convex sound box. Strings are plucked and pressed to change the pitch

African Lute Chad Skin below the strings on the gourd. Gourd resonator

Tar: Lute from Azerbaijan Belly is covered with ox pericardium membrane 24 movable frets of gut?

Harp –ngombi Central Africa plucked

Kora- Guinea ox tendon strings slid up and down for tuning notched bridge

Mbela- Musical Bow Central Africa What is the resonant cavity?

Sounding the string Plucking finger/plucker Sound is influenced by position of plucker Hammering Sound is influenced by weight of hammer, material of hammer and leverage of hammer. Bowed –stick/slip continuous excitation

Hammered/Plucked/Bowed Which one is which and how might you expect the sound would be different?

The importance of attack transients in sound identification Listening example 4.8 (Butler) Three sustained tones are presented, each with the attack transient (initial 60 millseconds) removed. Identify the instruments Listening example 4.9. First the sound of a violin (C4). Next the attack transient of that tone elongated to a hundred times its normal length through digital time expansion. Note this scratchiness makes it difficult for computer programs to transcribe music played by violins.

Mixed timbres Listening example 8.3. Starting with a French horn sound and ending with a clarinet sound. 11 short tones each shifted 10% further toward the clarinet tone. Listening example 8.4. Intermediate between piano and violin timbre. Both spectral mix, and attack envelope is intermediate.

Timbre and sound identification The tone color of an instrument Often used to describe spectral overtone mix. However attack transient, decay, vibrato all contribute to our identification of the instrument played. Auditory cues such as given in temporal changes are important.