PREMUTATION STAGE:  UNCHANGED VOICE CLASSIFICATION
 

 A. AGE:     Height of pre-pubertal period.  Unchanged voice reaches climax of beauty and "fullness."  Optimum period:  Grade 5 (Near end) to Grade 6.  Sometimes to early Grade 7.  Age span:  usually 10-11 years of age.

 B. VOICE DURING SPEECH:     Average Speaking Fundamental Frequency (SFF) A3 to C4 in the majority of cases.  "Light" voice quality.

 C. VOICE DURING SINGING:     Full, rich soprano-like quality.  Reaches its pinnacle of beauty, power and intensity during this time. Range expansion of the childhood voice at its maximum.  Breaks/shifts caused by inappropriate application of heavy mechanism in lower register (#2).  This problem often surfaces when singing from lower to upper part of the range.  Typically boys may sing too heavily in the lower range, and therefore shift quite noticeably when going to higher pitches.  Average range is A3-F5; tessitura is C#4-A4.

 D. ACOUSTICS:     Retains full spectrum of overtones in each tone.  Upper partial range (4100-8000Hz) not yet affected by maturation.  Full array of upper frequency amplitudes.  Average of 2-3 formants in lower partial range (80-4100Hz).and two for the upper partial range.  Dynamic range approaches healthy adult norms.

 E. PHYSIOLOGICAL:     Pre-pubertal, thus growth spurt not yet started.  Some "baby" fat on body frame.

 F. PART ASSIGNMENT:     Usually sings soprano part, but also capable of singing soprano II or alto.  Can easily sing in A3 to F5 pitch range.

 G. AGILITY:     Very flexible, agile voice with good capability for dynamic variation.

*Bracketed notes -- tessituras
 
 

EARLY MUTATION STAGE:  MIDVOICE I CLASSIFICATION

 A. AGE:     Initial pubertal period.  Lasts from 1 to 5 months on the average but can extend to 12 months or more.  Can begin in Grade 6; majority in Grade 7, between ages of 12 and 13.  Some may begin this stage as late as the eighth grade.  The onset of pubertal sexual and voice development can not be predicted with any degree of precision.

 B. VOICE DURING SPEECH:     Average speaking fundamental frequency (SFF) A3-B3 in the majority of cases  Light voice quality.  Very little perceptual change from the Unchanged period.  Sometimes breathier tone, especially above C5.

 C. VOICE DURING SINGING:     Variable loss of tonal clarity and "richness" in higher pitches, most notably in the C5-F5 range, but there is a noticeable increase in breathiness and constriction especially in upper pitch extremes.  Pitches can initially be sounded in the C5-F5 range, but there is a noticeable increase in breathiness and constriction..  Generally, tone quality is thinner and not as rich in harmonic partials in that range.  In the Cooksey, et al., study, subjects' average ranges decreased from 20.6 semitones in the Unchanged classification to 16.6 semitones in the Midvoice I Classification.  Average tessitura ranges decreased from 9.1 semitones to 8.1 semitones.

 D. ACOUSTICS:     There is a decrease in perceptual "richness" of the tone.  Generally, higher frequency formants are decreasing in amplitude in the lower and upper pitches of modal register.  Lower frequency formant amplitudes remain stable.  Both gross vocal volume and singing dynamic range are constant, still approaching healthy adult norms.

 E. PHYSIOLOGICAL:     Hormone secretions begin to trigger many physical changes, such as an increase in the amount of body fat, height and weight.  The vocal folds begin to lengthen and thicken.  Laryngeal cartilage structure begins to grow larger and change configuration, and muscles increase in size.  Seconday sexual development begins and the first appearance of pubic hair occurs.  Most of these changes are just beginning and are somewhat subtle in this stage.  The Cooksey, et al., Study showed strong increases, however, in total body fat, vital capacity, and weight.

 F. PART ASSIGNMENT:     Usually sings alto part in SATB music, but still has the most desirable vocal "color" and "power" in the mid-range area, D4-B4/C5.  Sometimes, SATB alto part is too low and the soprano part is too high.  Optimum pitch range is Ab3-C5.

 G. AGILITY:     Not as flexible or agile in upper range beause of increasing size of vocal folds.
 
 

HIGH MUTATION STAGE:  MIDVOICE II CLASSIFICATION

 A. AGE:     This stage is the height of mutational change.  Normal age is 13-14 years, but there are many exceptions.  Midvoice II's can be found in 6th grade and sometimes 5th grade.  A majority of boys have passed through this stage by the Spring of 9th grade year.  In the Cooksey, et al., Study, the average time boys spent in Midvoice II was 12-13 months.  There was, however, a large variance, ranging from 2 months to 19 months.  A majority of boys in this classification were found in grades 7-8, with the largest percentage found during Spring of the 7th grade year to Winter of the 8th grade year.

 B. VOICE DURING SPEECH:     Average SFF is lower and easily perceived when compared to Unchanged classification.  Voice quality for Midvoice II is noticeably "huskier," "thicker," and sometimes "breathy."  It is not as "light" as Midvoice I.  84% of the subjects in the Cooksey, et al., Study had average SFF's between G3-A#3, with the majority at about G#3-A3.  Beginning with this stage, the average SFF became stabilized at 3 to 4 semitones above the low terminal pitch (LTP) of the singing range.

 C. VOICE DURING SINGING:     This classification produces a unique voice quality that is "huskier" and "thicker" than Midvoice I, evidenced by an increase in noise levels in the upper partial range (4100-8000Hz).  Voices do not have the "richness" and "fullness" of adult-like tone.  Amplitude of spectral partials is much weaker when compared to the premutational stage.  In the Cooksey, et al., Study, pitch range decreased slightly to 15.5 semitones, but the range of tessitura remained about the same as Midvoice I.  Higher modal pitches were extremely unstable.  Transition zone (passagio) between modal and falsetto registers was F4-C5.  Falsetto and whistle registers emerged.  Falsetto began at G4-D5, with the majority beginning at about A4.  The maturation process has increased the instability of vocal coordination, particularly in regard to upper pitch range accuracy.  There is more stability in the lower pitch range.

 D. ACOUSTICS:     A decrease continued in upper partial range formant energy (amplitude/intensity) when the boys sustained lower and upper modal register pitches. There were further increases in noise components for this stage.  When compared to Midvoice I, noise levels of Midvoice II's almost doubled in their lower partial range (80-4,000Hz) when the boys sang lower and upper pitches in modal register.  Falsetto register was relatively free from constriction effects.  Gross volume and singing dynamic range increased slightly and continued to approximate healthy adult norms.

 E. PHYSIOLOGICAL:     The "shield" of the larynx, the thyroid cartilage, becomes more sharply angled, creating a relatively prominent, protruding "Adams Apple."  Bodily height, chest size , vital capacity, and weight continue to increase. There is a slight decrease in percentage of body fat.  Many boys show disparities in body proportions.  Maximum development now is occurring in primary/secondary sexual characteristics.  There are increases in the average amount of phonation time.  In the Cooksey, et al., study, phonation quotient was lowest of all the stages, indicating increased efficiency in vocal fold approximation.  Subjects produced surprising gross volume capabilities and this was reflected in increases in singing dynamic range measurements.

 F. PART ASSIGNMENT:     Skill in vocal part assignment by teachers and conductors is crucial for boys in this classification.  Alto parts often are too high; tenor parts too low.  Optimum pitch area is F3-F4 (G4).

 G. AGILITY:     Midvoice II's are not as agile when compared to unchanged voices.  Avoiding the upper pitch area (the most unstable part of their range), will help them avoid future hyperfunction, until healthy, efficient singing coordinations are established.  Range extension then may be possible by using the falsetto register to learn how to "melt" the register transitions.  If boys produce the falsetto register with excess effort, then use of the falsetto technique should be avoided or delayed until natural register corrdinations develop.
 

MUTATIONAL CLIMAX STAGE:  MIDVOICE IIA CLASSIFICATION

 A. AGE:     This stage of voice change coincides with the climactic period of puberty.  In the Cooksey, et al., Study, Midvoice IIA lasted an average of four to five months, but varied between 3 weeks to 10 months--even longer in a few cases.  A majority of the boys in this classification were in the 8th grade.  A significant upsurge occurred, however, in final month of the 7th grade.  There was a sharp decline in the number of Midvoice IIA's in the 9th grade.  The normal age span of boys for Midvoice IIA was 13-14 years of age, with a mean age of 13.6.

 B. VOICE DURING SPEECH:     In the Cooksey, et al., Study, the majority of average SFF's occurred at F3-F#3.  Voice quality is "huskier," "thicker" than Midvoice II, perhaps perceptually "thinner sounding."  These voices are very susceptible to hoarseness and abuse.  Register "breaks" are very apparent during this time.

 C. VOICE DURING SINGING:     High terminal and low terminal pitches are lower than Midvoice II, although the range span is about the same.  There is extreme instability in the upper pitch range where strain can occur easily.  Perceptually, listeners can hear some of the emerging baritone quality in the lower pitch range, but the upper range remains light and often displays increased breathiness and strain.  There is a very comon tendency toward hyperfunction, or "pushing" and the use of "heavy mechanism" during this stage.  Transition to falsetto can be extremely difficult, with some voices not able to sing in that register at all.  Due to changes in musculature of the larynx (and some muscle weakness in the arytenoid area), whistle register becomes more prominent.  Singers often have perceptual difficulties in matching pitch at times.  Part of this can be due to placement in the choir and confusion on the part of the teacher in assigning the voice to its appropriate pitch range.

 In the Cooksey, et al., Study, the extent of pitch and tessitura ranges remained about equal to Midvoice II.  High terminal pitches and low terminal pitches of their ranges were lower.  A majority of subjects showed register "lift points" between E4 and B4, but half the subjects changed to falsetto register on G4.  Most problematic transition area for registers was D4-G4.  Average pitch range was D3-F#4, and tessitura range was F#3 to C4/D4/E4.

 D. ACOUSTICS:     Noise and amplitude level statistics showed that this is the weakest, most vulnerable voice maturation stage.  By this time, constriction resulting from intrinsic laryngeal muscle strain was evident in many of the lower range partials.  General noise levels increased in lower partial range (80-4000Hz) of modal register, and this trend continued in succeeding voice classifications.  This data indicated a decreased energy (amplitude/intensity) throughout the singing range.  There was a slight increase in gross volume and singing dynamic range.

 E. PHYSIOLOGICAL:     In the Cooksey, et al., Study, there were dramatic increases in weight, and steady increases in height, chest size, waist size, and vital capacity.  Body fat percentages continued to decline.  Sustained phonation time increased.  Maximal development of primary/secondary sexual characteristics occurred. There was decreased vocal fold oscillation efficiency.

 F. PART ASSIGNMENT:     This is the most problematic classification for part assignment.  Most published music is unsuitable.  Optimum pitch range for singing is F3-D4.

 G. AGILITY:     Voice is weaker, less flexible, and a moderate pitch range for singing would be helpful for voice skill development  An emphasis on release of unnecessary neck-throat muscles and efficient laryngeal coordination is needed.  Cultivation of easy phonation will be valuable.  Be cautious in the use of falsetto register.

POSTMUTATIONAL STABILIZING STAGE:
NEW BARITONE CLASSIFICATION

[Please note that in these classification guidelines, the term "baritone" is chosen as a matter of convenience in the absence of a more satisfactory term.  In no way does the term indicate the presence of adult baritone characteristics.]

 A. AGE:     This classification represents the end of the most dramatic stage of voice change.  Many aspects of mutational processes are stabilizing.  In the Cooksey, et al., Study, the New Baritone designation lasted an average of 3-5 months, but varied between 4 weeks and 8 months.  A significant upsurge occurred in the number of boys in this classification during the last few months of 7th grade.  An even more dramatic upsurge occurred over the summer months between 7th and 8th grades.  There was a large percentage of boys in this classification in the 8th and 9th grades.  Normal mean age was approximately 14 years, but varied beween 13-15 years of age.

 B. VOICE DURING SPEECH:     In the Cooksey, et al., Study, a majority of the average SFF's occurred between C3-E3.  Lower pitches were quite evident.  Quality was "thin," and "light," compared to adult quality.  Voice quality was more consistently alike across individuals, i.e.,unique individual characterisics were not very prominent.

 C. VOICE DURING SINGING:     The New Baritone voice quality can be very firm and clear, but continues to sound "immature," "light," "thin," and lacking in the "richness" of a typical adult male voice.  There is less breathiness and constriction, generally.  There is very little vibrato.  Some listeners may "hear" this voice an octave higher than it actually is, and some listeners may hear it an octave lower than it is.  Usually, there is a much more stable transition area between modal and falsetto registers.  Falsetto register begins to stabilize in a majority of voices beginning around D4-E4.  The general transition area at C4-F4 is difficult for some singers.  During this classification, the voices of some boys may be able to sing reasonably well in their lower range, but as they attempt to sing toward a higher range, their falsetto register may "pop in" at G4, having skipped a number of pitches in between.  This "blank spot" is not uncommon.  With further maturation and guided experience over time, those pitches return.  Appropriately helpful vocalises that utilize falsetto register to "lighten" their upper range modal register sometimes enable a "return" of the "missing" pitches.

In the Cooksey, et al., Study, the extent of pitch range equaled Midvoice IIA (15.5 semitones), but tessitura range decreased to 7.4 semitones (Midvoice IIA was 8.1).  Voices were much more stable and consistent throughout the modal range, and falsetto register pitches became easier to produce.

 D. ACOUSTICS:     In the Cooksey, et al., Study, there was still no sign of a return of amplitude "strength" in upper frequency partials for lower and upper sustained pitches in modal register, as revealed in sonagraphs of the subjects in this voice classification.  These acoustic measures indicate the first emergence toward normal adult data, but still do not have the numerous harmonic partials and formant regions typical of the adult male voice.  Gross volume and singing dynamic range remained unchanged from the previous stage.

 E. PHYSIOLOGICAL:     In the Cooksey, et al., Study, increases in height, weight, chest size, vital capacity continued, with a generally correlated decrease in percentage of body fat.  There was a slight decrease in the duration of phonation on a single inhalation/ exhalation.  The phonation quotient was much higher indicating decreased vocal fold ocscillation efficiency.  That characteristic is normal for voices with emerging register differentiations, and also indicates maturity has not yet been achieved in changing voices.

 F. PART ASSIGNMENT:     Many bass parts are too low.  Optimum range for singing is Bb2 to C4-D4.

 G. AGILITY:     Lacks agility, flexibility, and often becomes heavy when fortissimo dynamics are called for.  Frequent "flatting" occurs when the voice is "overworked."  Cultivation of "lighter mechanism" and efficient breath energy in singing will enable increased agility.
 
 

POSTMUTATIONAL DEVELOPMENT STAGE:
DEVELOPING BARITONE CLASSIFICATION

 A. AGE:     This stage represents a marked tendency toward vocal maturity, and the emergence of a young man's personal vocal "signature."  Adult-like characteristics still are not apparent, but unique voice qualities begin to appear.  This stage is a period of gradual range expansion and growth in vocal anatomy.  The Developing Baritone Classification is prominent among 9th grade boys, and begins generally at 14-15 years of age.

 B. VOICE DURING SPEECH:     Majority of average SFF's now occur between A2-C#3, with average at B2.  Thicker, heavier voice quality now apparent.  More stability and consistency in voice production generally.  Low terminal singing pitch, in some cases, is "distancing itself" from average SFF.  In some cases low terminal pitch of singing range may be as much as 4-6 semitones lower than average SFF.

 C. VOICE DURING SINGING:     The trend established in the New Baritone stage continues, with quality becoming more clear and "focused," but still lacking in the greater richness associated with adult voices.  Voices at this age are not physically mature enough to produce the tone qualities, ranges, etc., that the adult categories of tenor, bass, and baritone can produce.  Note also that there is still little vibrato developing during this time, although unique resonance characteristics are beginning to appear.  Falsetto register is very clear and "focused."  Register transition area is slightly lower than New Baritone, but the majority of boys will begin falsetto register at D3,E3.  Upper range passagio area is C4-F4.  Upper register and falsetto register are easier to manage now.  In the Cooksey, et al., Study, pitch range began to expand rather significantly, from 15.5 semitones for New Baritones to 19.2 semitones.  Tessitura range also expanded from 7.4 semitones for New Baritones to 8.2 semitones for Developing Baritones.

 D. ACOUSTICS:     Noise in the lower partial range (80-4000Hz) continues to increase when boys sustain a lower pitch in modal register, but that lower partial range noise decreases when boys sustain a higher pitch in modal register.  Noise in the lower partial range decreases in falsetto register.  Phonational patterns are still somewhat erratic and motor control is still not secure.  Overall harmonic energy (amplitude) still does not approach adult norms or match those found in the unchanged voice.  The means of center of upper level formants in the upper partial range (as displayed by a lower pitch in modal register) remain about even with the New Baritone classification.  There is an increase in the means of centers of upper level formants when boys are sustaining a higher pitch in modal register.  The first and second average formant locations continue to decrease, indicating increased size of the vocal tract from physical growth, but they still do not approximate adult norms.  Gross volume and singing dynamic ranges increase slightly.

 E. PHYSIOLOGICAL:     Dense growth of pubic and auxilliary hair in body development.  Chest and shoulder dimensions continue to increase, as does weight, height, and vital capacity.  Dramatic increase in weight, but percentage of body fat remains stable.  Vocal folds have reached maximum length, and vocal tract cavities are approaching completed size and configuration.  Strong increase in phonation quotient indicating weaker glottal efficiency.  Apparently, voices in this stage still must develop much more before adult norms can be matched.

 F. PART ASSIGNMENT:     Can sing most bass parts, some may sing high baritone.  Optimum pitch area:  Bb2-A3.

 G. AGILITY:     Greater agility when compared to New Baritone, but physical development and "motor brain programming" must continue before adult agility can be approached.  More flexibility is available in the upper pitch range area and in transitions to falsetto register.  Again, cultivate ligher mechanism for modal/falsetto singing.  Many boys still will have a tendency to "push."