question: If amplitude compares to loudness and frequency to pitch, what's bass in scientific terms or in terms of the characteristics of the wave?
comment: "Bass" is just the low range of frequencies. If you "turn up the base," you're making lower frequencies louder and leaving middle and upper frequencies the same.
passages: Bass (sound)
  
  Bass ( ) describes tones of low (also called "deep") frequency, pitch and range from 16 to 256 Hz (C to middle C) and bass instruments that produce tones in the low-pitched range C-C. They belong to different families of instruments and can cover a wide range of musical roles. Since producing low pitches usually requires a long air column or string, and for stringed instruments, a large hollow body, the string and wind bass instruments are usually the largest instruments in their families or instrument classes.
  
  Section::::Use in composition.
   Section::::Musical role.
  
  When bass notes are played in a musical ensemble such an orchestra, they are frequently used to provide a counterpoint or counter-melody, in a harmonic context either to outline or juxtapose the progression of the chords, or with percussion to underline the rhythm.
  
  Section::::Musical role.:Rhythm section.
   Bass song
  
  A bass song is a piece of music that contains low frequency notes, or bass. Bass notes can be acoustic, but within the term "bass song" they are usually synthesized, typically sine waves or very similar. 
  
  Section::::Definition.
   In a marching band context, a bass run may consist of a several bar unaccompanied passage composed for the tubas and sousaphones which displays either rapid passages of notes or higher-register techniques. In New Orleans jazz, the tuba may provide a walking bass line similar to that of the double bass.
  
  Section::::See also.
  
  BULLET::::- Ground bass
  
  BULLET::::- Lament bass
  
  BULLET::::- Drum and bass
  
  Section::::External links.
  
  BULLET::::- - 244 million bass lines in F
  
  BULLET::::- An audio/video example of a walking bass line played on electric bass guitar
   As seen in the musical instrument classification article, categorizing instruments can be difficult. For example, some instruments fall into more than one category. The cello is considered a tenor instrument in some orchestral settings, but in a string quartet it is the bass instrument.
  
  Examples grouped by general form and playing technique include:
   To give a hint how all this works, consider three examples of the distinct senses that exist for the (written) word ""bass"":
  
  BULLET::::1. a type of fish
  
  BULLET::::2. tones of low frequency
  
  BULLET::::3. a type of instrument
  
  and the sentences:
  
  BULLET::::1. "I went fishing for some sea bass."
  
  BULLET::::2. "The bass line of the song is too weak."
   Though basslines may be played by many different types of instruments and in a broad musical range, they are generally played on bass instruments and in the range roughly at least an octave and a half below middle C (roughly the range of the bass clef). In classical music such as string quartets and symphonies, basslines play the same harmonic and rhythmic role; however, they are usually referred to as the "bass voice" or the "bass part".
  
  Section::::Instruments.
   In classical music, different forms of bass are: "basso concertante", or "basso recitante"; the bass voice of the chorus; the bass which accompanies the softer passages of a composition, as well as those passages which employ the whole power of the ensemble, generally played by the violoncellos in orchestral music; "contrabass" (“under bass”), is described as that part which is performed by the double basses; violoncellos often play the same line an octave higher, or a different melodic or rhythmic part which is not a bassline when double basses are used; "basso ripieno"; that bass which joins in the full passages of a composition, and, by its depth of tone and energy of stroke, affords a powerful contrast to the lighter and softer passages or movements.
   Bass
  
  Bass or Basses may refer to:
  
  Section::::Fish.
  
  BULLET::::- Bass (fish), various saltwater and freshwater species
  
  Section::::Music.
  
  BULLET::::- Bass (sound), describing low-frequency sound or one of several instruments in the bass range:
  
  BULLET::::- Acoustic bass guitar, with a hollow body
  
  BULLET::::- Bass clarinet, a clarinet with a lower sound
  
  BULLET::::- Bass cornett, a low pitched wind instrument
  
  BULLET::::- Bass drum, a large drum
  
  BULLET::::- Bass flute, an instrument one octave lower than a flute
  
  BULLET::::- Bass guitar, with a solid body and electric pickups
  
  BULLET::::- Bass recorder, an instrument one octave lower than the alto recorder
   The type of rhythmic pulse used in basslines varies widely in different types of music. In swing jazz and jump blues, basslines are often created from a continuous sequence of quarter notes in a mostly scalar, stepwise or arpeggio-based part called a "walking bass line". In Latin, salsa music, jazz fusion, reggae, electronica, and some types of rock and metal, basslines may be very rhythmically complex and syncopated. In bluegrass and traditional country music, basslines often emphasize the root and fifth of each chord. 
   BULLET::::- A bass horn, such as a tuba, serpent, and sousaphone from the wind family and low-tuned versions of specific types of brass and woodwind instruments, such as bassoon, bass clarinet, bass trombone and bass saxophone, etc. (less common usage)
  
  BULLET::::- Keyboard bass, a keyboard alternative to the bass guitar or double bass (e.g. the Fender Rhodes piano bass in the 1960s or 13-note MIDI keyboard controllers in the 2000s)
  
  BULLET::::- Washtub bass, a simple folk instrument
   A bassline (also known as a bass line or bass part) is the term used in many styles of music, such as jazz, blues, funk, dub and electronic, traditional music, or classical music for the low-pitched instrumental part or line played (in jazz and some forms of popular music) by a rhythm section instrument such as the electric bass, double bass, cello, tuba or keyboard (piano, Hammond organ, electric organ, or synthesizer). In unaccompanied solo performance, basslines may simply be played in the lower register of any instrument such as guitar or piano while melody and/or further accompaniment is provided in the middle or upper register. In solo music for piano and pipe organ, these instruments have an excellent lower register that can be used to play a deep bassline. On organs, the bass line is typically played using the pedal keyboard and massive 16' and 32' bass pipes.
   Section::::History.:Hector Boece.
  
  Hector Boece offers the following description (original spelling):
  
  Section::::History.:Royal visits.
   BULLET::::- Double bass from the viol or violin family (usually the instrument referred to as a "bass" in European classical music and jazz. Sometimes called a "string bass" to differentiate it from a "brass bass" or "bass horn", or an "upright bass" to differentiate it from a "bass guitar")
  
  BULLET::::- Bass guitar and acoustic bass guitar, instruments shaped, constructed and held (or worn) like guitars, that play in the bass range. The electric bass guitar is usually the instrument referred to as a "bass" in pop and rock music.
   Basso continuo was an approach to writing music during the Baroque music era (1600-1750). With basso continuo, a written-out bassline served to set out the chord progression for an entire piece (symphony, concerto, Mass, or other work), with the bassline being played by pipe organ or harpsichord and the chords being improvised by players of chordal instruments (theorbo, lute, harpsichord, etc.).
  
  "The bass differs from other voices because of the particular role it plays in supporting and defining harmonic motion. It does so at levels ranging from immediate, chord-by-chord events to the larger harmonic organization of a entire work."
  
  Section::::Instruments.
   Transient (acoustics)
  
  In acoustics and audio, a transient is a high amplitude, short-duration sound at the beginning of a waveform that occurs in phenomena such as musical sounds, noises or speech. It can sometimes contain a high degree of non-periodic components and a higher magnitude of high frequencies than the harmonic content of that sound. Transients do not necessarily directly depend on the frequency of the tone they initiate.
  
  Transients are more difficult to encode with many audio compression algorithms, causing pre-echo.
  
  Section::::Sonar.
   List of basses in non-classical music
  
  The bass singing voice has a vocal range that lies around the second E below middle C to the E above middle C (i.e., E–E). As with the contralto singing voice being the rarest female voice type, the bass voice is the rarest for males, and has the lowest vocal range of all voice types. However, the bass voice is determined not only by its vocal range, but also by its timbre, which tends to be darker than that of a baritone voice.
   Basso profondo
  
  Basso profondo (Italian: "deep bass"), sometimes basso profundo or contrabass, is the bass voice subtype with the lowest vocal range.
   Bass guitar
  
  The bass guitar (or simply bass) is a plucked string instrument similar in appearance and construction to an electric or an acoustic guitar, except with a longer neck and scale length, and typically four to six strings or courses.
   Sub-bass energy is popular in dance music, where the low frequencies involve energy from the kick drum (bass drum), the bass guitar and electronic synthesizers and drum machines. Particular genres such as house music, drum and bass and dubstep often feature a bassline that consists mainly of sub-bass frequencies. Much experimental music uses sub-bass, in particular drone music, where the majority of the sound can often be in the sub-bass range. Often, hip hop and rap songs feature prevalent sub-bass. The pedal keyboard range on pipe organs also often extends into the sub-bass range; the bottom note of a 16′ stop is typically tuned to 32 Hz (C), a 32′ stop at 16 Hz (C).
   Section::::Organisation.
   Section::::Riffs and grooves.
  
  Basslines in popular music often use "riffs" or "grooves", which are usually simple, appealing musical motifs or phrases that are repeated, with variation, throughout the song. "The bass differs from other voices because of the particular role it plays in supporting and defining harmonic motion. It does so at levels ranging from immediate, chord-by-chord events to the larger harmonic organization of entire work." 
   A bass run (or "bass break") is a short instrumental break or fill in which the bass instrument (such as an electric bass or a double bass) or instruments (in the case of a marching band) and the bassline are given the forefront. The bass part for a bass run often differs from the usual bass accompaniment style, in terms of the register, timbre, or melodic style that is used, or the number of notes per beat which are played.
   The Bass numbers describe the minimal injective resolution of a finitely-generated module "M" over a Noetherian ring: for each prime ideal "p" there is a corresponding indecomposable injective module, and the number of times this occurs in the "i"th term of a minimal resolution of "M" is the Bass number formula_2.
   Section::::Composition.
  