DAVID A JAFFE Ten Criteria for Evaluating synthesis Techniques part1

DAVID A JAFFE Ten Criteria for Evaluating synthesis Techniques part1

1. 10 EVALUATION CRITERIA: PARAMETRIC 1 - 5

   • how INTUITIVE are the parameters
     • STRONG -MAPPING control parameters to musical parameters
       • EGS STRONG
         • dynamics
         • articulation
         • ANALOG SYNTHESIS LPF maps BW / AMP less brightness with softer dynamics
           • LOW VALUES = PP
             • softer notes = lower AMP + less high freq
           • HI VALUES = FF
             • louder notes = higher AMP + more high freq
               • physical nonlinearities become more prominant as instr are played louder
           • ADJUSTABLE ON note-by-note basis: DECOUPLES
             • DISTANCE - FUNCTION OF LOUDNESS
             • DYNAMICS - FUNCTION OF BRIGHTNESS
     • WEAK UNMAPPED mathematical variables
       • EGS WEAK
         • Changing FM INDEX OF A CASCADE MODULATOR SLIGHTLY
           • DRASTIC, DIFFICULT TO PREDICT CHANGE IN TONAL QUALITY EG FROM DRUYM TO WOODBLOCK
             • Annoying for composers
             • Problematic for performer - in live situ
   • how PERCEPTIBLE are parameter changes
     • more parameters - weaker the impact of each
     • STRONG
       • sig. ch. = obvious audible effect
       • too strong = uncontrollable
       • e.g. a low pass filter proportional to cutoff freq (expon or linear)
     • WEAK
       • sig. ch. = barely audible
       • too weak = fruitless arbitrary alterations
       • METAPARAMETERS
         • EG1a
           • Used to enable more intuitive and perceptible changes to synthesis methods - e.g. brightness to each array element freq, AMP array, brightness can be applied across each element of the array
             • ActualAmps[i]=Amps[i]*MAX(brightness, 0.001)^log2(MAX(Freqs[i],100.0)/50.0)
           • addSyn used as inv FFT the LPF - log2 and MAX() rtns max of its args,
         • EG1b
           • addSyn * LineSeg - multidimentional timbral space
             • values added to scale addSyn partials producing complex interpolations (mcNabb 8f1)
         • EG2
           • Digital Sampling (*ID synth tech). edit 1 sample no effect used wtih HYBRID PARAMETERIZED PROCESSING MODULES eg filters, amp envs etc
       • EG1 addSyn - ch. amp of each partial could be weak for hi harmonics
   • how PHYSICAL are parameters
     • cntrls synthetic instr. in same way as real-world instr. is cntrled
       • EG1
         • Violin - waveguide model bow pressure/velocity (smith 92)
       • EG2
         • Clarinet mouth breath pressure parameter (cook 88)
     • ADV
       • 1 good at: Complx behaviours at unstable moments in a tones evolution eg attack and transistions
       • 2 no need for const. analytical modelling/database player/composer/implemntor neednt understand what happens in output wav during attack/trams te physical nature of parameter cuases the correct result
     • DIS
       • For nonexpert players - nonphysical INTUITIVE cntrls - more appropr.
     • for non-phys. synth parameters (eg. amp of addSyn partial -
       • SOLUTION - MAP WITH META- PARAMETER
       • PROB - need thorough ACOUSTICAL KNOWLEDGE to defne mapping adquately
   • how WELL BEHAVED are the parameters
     • EGS - LINEAR TECHNIQUES
       • when CNTRL RATE = SLOW RELATIVE TO AUDIO SR
         • STRONG
           • STRONG - PROPORTIONAL change to sound wth cntrler
           • FILTERS - GOOD DURING TRANSITIONS
             • PERRY COOK WAVEGUIDE-BASED VOCAL SYNTH MODEL 90
               • MODELS vocal tract - series waveguide filters
                 • Each waveguide filter = xsect. of vocal tract
                   • each vowel = physical interpretation - 1 or sev section diameters: shrink / incr.
                 • interpolating between vowels corres. dir. to real-world spatial interpolation
           • Each intermediate val. have INTUITIVE PHYSICAL interpretation = WELLBEHAVED
       • CNTRL parameters change RAPIDLY - ENERGY IS INECTED INTO TH SSYSTEM WTH POSS OF UNPREDICTABLE UNEXPECTED RESULTS
         • WEAK
           • WEAK - small parameter ch - WILD, UNPREDICTABLE sonic outcome
           • EG 3 NONLINEAR FB TECH (Mcintyre/ woodhouse 83
             • nonlin. FB in phys. mod. wind instr.
             • EXTREME SENS. to INITIAL COND.
               • DEF. OF CHAOTIC SYS.
                 • can be modelled in REGIONS of its STATE SPACE for PREDICABLE EFFECTIVE HAEVIOUR
         • E.G. AUDIO RATE AMPLITUDE SCALING
           • E.G. SINUSOIDAL
             • AM - 2 sidebands are produced for each componente in original signal = NONLINEAR - SIDEBANDS ARE AT FREQ CORRESONDING TO THE FREQ OF EACH COMPONENT PLUS OR MINUS THE MOD FREQ
           • E.G. NON- SINUSOIDAL
             • EVEN MORE CMPLX than above
         • EG2 FILTER STRUCTURES THAT BECOME UNSTABLE DURING TRANSITIONS FROM 1 SET OF COEFFICIENTS TO ANOTHER
   • how ROBUST is the sound's IDENTITY
     • HOW WELL SOUND RETAINS ID IN CONTEXT OF VARIATION
       • True rep. of expres.. instr. = FAMILY OF RELATED SOUNDS req.
       • not repr. of 1 note
     • Inst. Def. wth grt variety in context of particular sounrce ID
     • synthesis NOT a snapshot = expressive OVER TIME
     • EG Good
       • PHYS MOD
         • PhM Waveguide
           • Karplus- Strong String
             • rich expr. vocab. not loose ID
               • e.g. pick pos, string: flex, thickness, dyamics, decay char
             • ks 83 / jaffe J smith 83
       • SMPLING Power / flexib. CAN BE grtly enhan.
         • Multiple rec. xros
           • BW
           • dynamic contours
           • attacks
             • Vibrato
           • max multiple guises
         • filters = dynamics
         • linear interpolation for timbral variety eg thru BW n.b. take care to MATCH PITCH AND PHASE
         • as many samples per inst. as memory allows - more guises covered more expressive result
     • EG POOR
       • Pure Sampling
         • add var. to one sample = 2D cardboard sound
           • e.g. articulation, dynamics, timbre falls over if pused lightly in any direction
       • 1 pitch
     • sampling = challenge + opportunity

2. identity synthesis technique = DIGITAL SAMPLING. Each SAMPLE is a PARAMETER itself