PH 105 Dr. Cecilia Vogel Lecture 17

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= 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 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.