What is this thing called "barbershop harmony?" Essentially, it's a unique four-part close harmony style, most often performed a cappella, based on performance practices common in the American south during the late 1800s and early 1900s. Today, the barbershop "umbrella" covers a wide variety of musical genres and repertoire, but still holding on to certain key characteristics of harmony, structure and style. The international Barbershop Harmony Society, Sweet Adelines International, and Harmony Inc. organizations are dedicated to the preservation and promotion of this wonderful art form. Some excellent information about the history and evolution of barbershop singing can be viewed here:

How does barbershop differ from traditional choral singing? It doesn't... much! The posture, breathing, and basic tone are exactly the same as for traditional choral (or even bel canto) singing. Any differences in the sound have more to do with stylistic elements. Some of the main points have been listed below: (Warning to novice musicians: some heavy-duty music theory terminology follows! Ask your teacher if you have questions about any of the terms used.)

• As a folk/pop style, vowels tend to be a bit brighter and more forward than in classical music, and pronunciation of consonants tends to be more relaxed and colloquial. (Example: "little" would be pronounced closer to "liddle," and final consonants may be dropped on words like "and.") This is a fairly simple adjustment to make, and is similar to a technique you might adopt to sing a spiritual, folk song or jazz piece.
• Rhythms, especially in ballads, tend to be very loosely interpreted. Barbershop singing makes extreme use of rubato, most commonly to emphasize really "tasty" chords or to support the emotion of the text being sung. A "conversational" approach to rhythm is often the goal.
• Barbershop has a unique chord vocabulary. Dominant 7th chords (often called "barbershop 7ths") are prominently featured, and are often used to create strong harmonic progressions based on the circle of 5ths. Minor 7th chords and diminished 7th chords are also common, as are 9th chords (with the 5th omitted), while major 7ths, augmented chords, "add 2," "sus 4" and other chords commonly found in pop and jazz are rare. Most pieces are in major keys, and even minor pieces will often end on a Picardy 3rd so that we get the ringing overtones of major harmony.
• Traditional Baroque rules of voicing and voice leading don't apply. Every note in the melody is typically harmonized by a four-part consonant chord, almost always in root position or 2nd inversion. Voice crossing is common (especially between the Lead and Baritone voices), as are parallel fourths and 5ths, and leading tones and 7ths often do not resolve in the ways typically expected. Singing barbershop (particularly the baritone part) is some of the best ear-training experience you'll ever have!

Speaking of Lead and Baritone, what's the deal with the barbershop voice parts? How do I know which part to sing? Barbershop voice parts work a bit differently than standard choral parts. Essentially, it breaks down like this:

For the men - Lead and Tenor parts are written on a Treble Clef staff, but sound an octave lower than written (in the male range). Baritone and Bass parts are written on a bass clef staff and sound as written. The following are guidelines for choosing your specific voice part:

• TENOR - Sings predominantly in a falsetto or light head tone, harmonizing above the lead. Practical range is a written G above middle C (sounding as the G below middle C) to high G above the staff (sounding as a G above middle C), occasionally extending as high as Bb (or sometimes higher!) above the staff. This part is often sung by choral baritones or even basses with a well-developed falsetto or head voice, although choral Tenor I singers with good facility up high may occasionally sing barbershop tenor. Unchanged or cambiata voices (boys who have not yet completed puberty and who sing male alto parts in choir) should also choose this voice part.

• LEAD - As the name suggests, this part carries the melody most of the time. Practical range is a low Bb (written below middle C, sounds an octave lower) to a high F# on the fifth line (sounds as an F# above middle C), and occasionally higher. The Lead part is typically sung by choral Tenor I and Tenor II singers, or even Bass I/Baritone singers who are comfortable in their upper register.

• BARITONE - Similar in range to the Lead, Baritones must have a good ear, as they typically have parts which require a lot of voice crossing with the Leads and challenging intervalic leaps. Choral Tenor II and Bass I (Baritone) singers might choose to sing this voice part.

• BASS - Similar to its choral counterpart, the barbershop Bass provides the harmonic foundation of the ensemble. A barbershop Bass should have a low G (first line) at minimum, with a solid low F below the staff (or lower) preferred.

For the women - Lead and Tenor parts are written on a Treble Clef staff and sound as written. Baritone and Bass parts are written on a bass clef staff, but sound an octave higher than written (in the female range). The overall range/tessitura of the voice parts is often dependent on the bottom range of the bass - a bass with solid lower notes allows the whole quartet to sing lower. The following are guidelines for choosing your specific voice part (from Harmony Inc. and Sweet Adelines International sources):

• Lead is the melody and is sung mostly in the range between D above middle C and 5th line F, although the range may occasionally extend as low as A below middle C. This part is a good choice for a mezzo-soprano or choral Soprano II or Alto I with a clear middle register.
  

• Tenor is a harmony part sung consistently above the lead. Although tenor is the highest voice in barbershop harmony, it should not be confused with soprano of conventional singing groups. The tenor should have a light, sweet, pure tone that will compliment but not overpower the lead voice. Typical range is C above middle C to high A above the staff. A good choice for sopranos who can sing lightly in the upper register.
  

• Baritone covers approximately the same range as lead. The baritone harmony notes cross the lead notes; sometimes sung below and sometimes above. Baritones must constantly adjust their balance to accommodate their position in the chord, and should be good harmony singers with good ears. Again, strong mezzos and altos are good candidates for this part.
  

• Bass singers should have a rich, mellow voice and be able to sing the F flat below middle C easily. (In more mature singers, a low Eb is even better!) Basses should not be confused with the alto of conventional groups. Many altos can sing the bass part, but others are much better suited to lead or baritone, depending on range and vocal quality. Alto IIs who are extremely solid in their lower register should opt for bass.