OUTLINE Resonances of string instruments Brass Instruments Lip reed Closed tube Effect of bell Registers timbre Playing scales
String Instrument Review Fundamental freq —pitch determined by string. many harmonics produced by string, too. Spectrum — timbre Resonances of bridge, plates, air cavity. enhance certain harmonics.
Timbre Demo A-string Expect strong 110 &220 near resonances (fig 10.31) play C3 (131 Hz): 1 st harm ___, 2 nd ___ G-string Expect strong fundamental and 2 nd harm? 196 Hz and 392 Hz near resonances at 200 & 400 Hz ( folk only ) B-string f1= 246.94 Hz, ___ and ___ harmonics near 250 Hz and 550 Hz resonance of classical
Brass Instruments An instrument is considered to be in the brass family if the source of disturbance for the sound is a i.e. the lips buzz in the mouthpiece to excite sound waves in the air inside Sound of a brass instrument is affected by sound source (_____), resonances (___________), and radiation (_____)
Feedback Can control pitch of lip reed by changing Hard to do with precision. Even harder to maintain. Once lips have started the air vibrating the pressure variations in the air This is called positive feedback.
Air Column Resonances The lip end of a brass instrument is a The cylindrical tube of a brass instrument WOULD resonate at freq’s Where v = speed of sound in air L = length of tube n = only odd integers BUT…..
Bell Effect Adding a bell and mouthpiece makes the instrument longer, ________ all the resonant freq’s. But the high freq resonances are affected more, so the resonances get
Bell Effect Resonances without bell and mouthpiece Resonances with bell and mouthpiece 1 35 ratio 5/3 = 1.67 ratio 3/2 = 1.5
Bell Effect Adding carefully tuned bell and mouthpiece makes resonances other than the lowest approximately, even and odd, of a The “lowest” note of brass instrument, is not the fundamental frequency, but 2 nd partial. Lowest resonance— called “pedal tone” not often used, overtones not harmonic.
B 3 b (233 Hz) uses 2 nd resonance of tube Open Notes of Brass played note (fundamental of lip buzz) harmonics of played note (harmonics in lip buzz)
F 4 uses 3 rd tube resonance 349 Hz (which is a fifth above B 3 b ) Open Notes of Brass played note harmonics of played note
B 4 b uses 4 nd tube resonance at 466 Hz (which is an octave above B 3 b ) Open Notes of Brass played note harmonics of played note
Can play B 3 b, F 4, and B 4 b on trumpet by exciting different of the same These are the open notes of three different registers higher registers have weaker overtones Bugle can only play these notes. Registers
Trombone can play whole chromatic scale by changing the length of the tube. Slide a piece of tube out making it To go one semitone lower, the length of the tube should increase by 1/18 its current length. The lower you go, the fig 11.11 Slides
There are seven positions for trombone slide Position 7 gives you E 2 in the lowest Positions 6-1 let you go up 1-6 semitones. What if you wanted to go up 7 semitones? That’s a Can play that in 7 th position Using slide in 2 nd register, then in upper register. gets you all the way up to B 3 b Seven Positions
Trumpet can play whole chromatic scale Pressing a valve brings an additional piece of tube into the airway making it One valve makes it one brings in extra 5.9% (about 1/18) of tube length. Another makes it two brings in extra 12.2 % of tube length. Yet another makes it three brings in extra 18.9% of tube length. Valves
With only three valves, how do you go down more than 3 semitones? one + three = two + three = one + two +three = 7 semitones is a can be played in Four semitones is more than logarithmic, not linear. Third valve tubing may have a slide, so it can be adjusted. Or you can adjust lip freq. Three Valves
Brass Demo Listen to timbre. Observe spectrum. Play in different registers. What technique is used? What intervals can be played with same slide or valve position? (expect 2 nd, 3 rd & 4 th harmonics; factors of 3/2 or a perfect fifth and of 2 or an octave) Change of timbre with register Play chromatic scale using slide/valves. which slide positions are closer together? Why?
Summary Closed tube resonances, are changed by bell & mouthpiece, brass instrument resonates at 2 nd, 3 rd, 4 th, etc harmonics of missing fund. registers: 3 rd harmonic is up a fifth from 2 nd 4 th harmonic is up an octave from 2 nd Trombone adds length with 7 positions of slide. Trumpet adds length with 3 valves.
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