Why is it that notes "start" with C? In key signatures, for example, C Major is the basis and accidentals are added for all other key signatures. I know that the musical alphabet starts with A and goes to G, so why is C the base note of standard notation and keys? Why isn't A the basis?
Notes do not "start" with C; C major is just the easiest major key to notate in modern notation. The concept of a major key came about long after letters were assigned to the notes. Before there were major (and minor) keys, people used modes, usually just using the notes of the modern white keys and starting and ending in different places. The Ionian mode (which became modern major) was a late addition to the modes.
So it's historical accident that C major is treated as "basic."
As is common with these sorts of questions, there's a lot of speculation in various answers. But, if the question is at least historically why C is the central note of the modern musical scale system, there's one specific and rather clear origin point: Gioseffo Zarlino's Dimostrationi harmoniche of 1571.
Zarlino was perhaps the most influential music theorist of the 16th century -- one of the first to primarily disseminate his ideas in a vernacular language, Italian (rather than the scholarly Latin, where the ideas would be less likely to spread to your average less-educated musician). For several reasons discussed below, Zarlino decided the renumber the standard modes at the time and to place the mode with the C final (generally represented by the scale C-D-E-F-G-A-B-C) as the first mode, giving it a primary place in the system of music theory for the first time.1
The Central Role of D as the Final Note of the "First Mode"
Before we discuss this new development, the context of the older music theoretical systems is important to note. The original diatonic scale was derived from a Greek model that extended down to a note called proslambanomenos, the lowest note which often represented an open (unstopped) string on a string instrument.2 In the medieval period, around the year 1000, letter notation for notes became common, and this lowest note was given the name A, with the other letters of the alphabet used in order to ascend the scale. This note A had no particular importance in medieval music theory -- other than being the lowest possible note -- as it had been borrowed in from an ancient Greek scale system. (In the ancient Greek system, the A an octave above did have a central place as a sort of "middle note" (mese) in the scale around which the rest of the scale was built.)
Instead, if anything, the central note of medieval music theory was arguably D. Before letter notation even became common, in the late 8th century books called "tonaries" were invented to classify chant melodies, and they labeled the "first tone" for melodies that had a pattern around the final note with a whole tone below, a whole tone above, and a semitone above that (followed by another whole tone). Using letters for note names, we can see that conforms to the note pattern C-D-E-F-G, with D as the final note that melodies tend to cadence on.
Why D? Not again because it was anything particularly special. Its main advantage was that it was first in an ascending order of classification of modal final notes. Chants ending with the pattern above were originally in the "primus tone," those which had a pattern conforming to what we'd think of as the note E now were labeled "secundus," those with F were "tritus," and those with G "tetrardus." Essentially, the first, second, third, and fourth "tones" (later called "modes") were based around cadential notes that were equivalent to what we now call D, E, F, and G.3
The modal system was gradually systematized over many centuries during the medieval period and the early renaissance. But the mode that placed D as the final was pretty consistently referred to as the "first mode," just because it happened to be the lowest note in the scale that served as the basis for a mode.
The Importance of C, F, and G as the Lowest Note of Hexachords
Over the centuries, other notes in the musical scale also began to assume some importance. In the 11th century, a music theorist named Guido of Arezzo invented a number of essential music elements, including the standard staff notation and the predecessors of clefs.4 While clefs originally came out of the important location of the semitone in the scale (below the notes F and C), they eventually also became associated with another of Guido's inventions: the hexachord.
It's unclear what the original inspiration of the musical unit of the hexachord was. By this point, the scale had been extended another whole step below that A to a note known as Gamma. Beginning on that note and ascending through the first six notes (Gamma-A-B-C-D-E) gave a pattern of whole tones and semitones: W-W-S-W-W.
Guido noted that this pattern could occur at several other places in the standard scale, including on G-A-B-C-D-E in other octaves and on C-D-E-F-G-A. At the time, again due to complexities borrowed from the original Greek scale system, B-flat was the only "accidental" possible in the medieval scale. Thus, the hexachord pattern of W-W-S-W-W could occur in one other place in the scale: F-G-A-B♭-C-D.
As noted, F and C already had assumed an importance in the scale due to placement of semitones directly below them. (Before standardized clefs, knowing where the semitone was would be an essential part of reading music and orienting oneself to the placement of the notes of the scale.) The hexachord patterns emphasized by Guido became the basis of solmization, originally with the syllables Ut-Re-Mi-Fa-Sol-La, and the placement of Ut also emphasized F and C, along with G.
The Twelve-Mode System and C as a "Legitimate" Final
The hexachordal system was the foundational system for learning how to sing for over half a millennium. It's possible that the placement of "Ut" in that system perhaps created a tendency to emphasize "major sounding" modes. Or perhaps there were other stylistic trends (accelerated with the new emphasis on tertian harmonies in the 15th century) that led to more compositions in modes that were based on C, F, and G.
In any case, by the early 1500s, it was pretty clear that a lot of actual music was being written using what we'd call the "major scale" today (or in some cases a Mixolydian scale that would often using a raised leading tone at cadences). While such music could be written using a central note of G (and musica ficta assumed at cadences, as F♯ was not a "proper" note of the scale yet) or written on F, using the B♭ that was part of the scale, some music theorists felt there needed to be a place for a legitimate mode based on the note C. Prior to this time, music using a C-D-E-F-G-A-B-C scale would have been viewed as a transposition of the Lydian alternate scale using B-flat, i.e., F-G-A-B♭-C-D-E-F.5
Heinrich Glarean's Dodecachordon of 1547 thus proposed the addition of A and C to the list of standard final notes for modes (beyond the D, E, F, and G mentioned above that went back to the first modal classification systems in medieval music nearly 800 years earlier). The note B was rejected as a final for standard modes mainly because it lacked a perfect fifth above the final. The new system of modes thus went in the order D, E, F, G, A, C, for a total of twelve modes, two numbered on each note.6 D was still the traditional "first mode" and beginning of that system, while the modes on C were 11 and 12, the very last.
Zarlino, Tuning Scales, and the Primacy of C
This is the world Zarlino came into: a world with competing systems. Modes began their numbering on D, but hexachords were based on C, F, and G. And more and more popular music was being written using C and F as finals.
In his Dimostrationi harmoniche of 1571, Zarlino thus proposed a way of bringing all of this together into a more coherent system. The first mode would be numbered beginning on C.7 Several reasons were given, but for Zarlino, the quest to place C (and what we now call the major scale) at the center of his modal system began with his new approach to tuning.
In medieval theory, priority in tuning systems was given to what we now think of as "Pythagorean tuning," a system that emphasizes ratios 2:1 (the octave), 3:2 (perfect fifth), 4:3 (perfect fourth), and 9:8 (one of the standard whole tone ratios dating back to ancient Greece). But the practical use of "sweeter" major thirds with ratio 5:4 (along with minor thirds with ratio 6:5) instead of the Pythagorean ditone (81:64) composed of two 9:8 whole tones led Zarlino to advocate for a new approach to tuning. Rather than the ancient Greek tetractys, which stated that consonances could be composed of ratios with whole numbers up to 4 (thus including the octave, perfect fifth, and perfect fourth as stated above), Zarlino argued for a new concept of the senario, based on the number 6 as the limit for consonance. Thus, the 5:4 major third and the 6:5 minor third were admitted to the realm of harmony in a new way.
What does this have to do with the scale C-D-E-F-G-A-B-C? Well, in dividing up the octave to demonstrate this new emphasis on sweet 5:4 thirds, Zarlino chose that particular sequence of notes and division of scale. It also had the advantage of being built around a central tetrachord of E-F-G-A in a particular ratio that corresponded to a tetrachord Ptolemy had advocated in ancient Greek tuning systems, thus allowing Zarlino to bring together modern practical tuning with sweet thirds and ancient authority.8
Ultimately, Zarlino gave a number of reasons for viewing the octave scale based on C as the first (and primary) one:
- The C-D-E-F-G-A-B-C scale exemplified Zarlino's new tuning system and use of harmonic number for the primary ratios that underpinned his central scale. He argued that this particular division of the octave was therefore the most "natural."
- This word was not a coincidence, as C was the bottom note of the so-called "natural" (naturalis) hexachord. As mentioned above, C, F, and G were all used to begin hexachords. But F required the use of B♭, known as B mollis ("soft B"), and G required the use of B♮, known as B durus ("hard B"). (The shape of our modern flat and natural signs derives from the rounded and square shapes of the "soft" and "hard" Bs.) The C-based hexachord was natural because it avoided all of this problem of choosing a B. It just had the notes C-D-E-F-G-A and thus had a kind of superiority relating in some ways to notions of ratios and harmonic number relating to the scale as well.
- All of the modal finals could be arranged in ascending order within the Guidonian hexachord based on C, i.e., C-D-E-F-G-A. Recall that the original primus mode began on D simply because it was the lowest among the four original finals of D-E-F-G. Rather than having a gap and skipping over B, as Glarean's 12-mode system did with D-E-F-G-A-C, Zarlino recognized the simplicity of a system that simply walked up the scale with the numbered modes. (A related but somewhat more technical point had to do with the arrangement of "species" of octave, i.e., the different locations where semitones could fall in relation to the whole tones. Placing C first also allowed cycling through the various octave species that tended to be enumerated in music theory treatises of the time without interruption.)
- Even better, the actual six finals of the mode in order would now make up their own uninterrupted diatonic hexachord in order: C-D-E-F-G-A (i.e., Ut-Re-Mi-Fa-Sol-La). This served to tie Zarlino's system into the authority of Guido's hexachordal system in a rather fundamental and intuitive way.
- Lastly, Zarlino was sensitive to the fact that ancient Greek place name terms like "Dorian" and "Phrygian" had been mistakenly mapped onto the medieval modal system. (For example, the first mode was called "Dorian," but the ancient Greek conception of Dorian was actually closer to the intervals of what we'd call a Phrygian scale. Medieval music theory was often based on misunderstandings and mistranslations built on top of other misunderstandings.) According to some ancient sources, the Dorian, Phrygian, and Lydian scales were each a whole tone apart. So Zarlino decided that perhaps it would be better to map "Dorian" -- a name for a mode which had been viewed as a central mode both by the Greeks and renaissance theorists as central -- onto the C-C octave instead. This tended to accord better with some ancient Greek accounts of the character of Dorian, in Zarlino's view. (Same thing with the supposed ancient characters of Phrygian and Lydian, which for Zarlino perhaps mapped better onto the D-D and E-E octave scales respectively.)
In addition to all of these explicit justifications, there's something to be said for the general sound and popularity of the C-based major scale as the first mode. After Zarlino renumbered the modes, his published music that grouped pieces by mode tended to emphasize compositions that we'd now say sound like they are in "C major." This wasn't so much a theoretical argument as much as a practical benefit that Zarlino seemed to make use of.
After Zarlino: A New System of Keys
Zarlino's renumbering of the modes wasn't universally adopted. It gained some currency, particularly among French theorists. But many German and Italian theorists would continue using Glarean's numbering of the 12 modes (or the original numbering of only the 8 modes) well into the 1700s. (Zarlino's renaming of the modes with C being called "Dorian" proved even less popular, though that was perhaps also partly because Zarlino himself downplayed the ancient Greek names as he knew they had a long history of misappropriation by others. Instead, he advocated for a strictly numerical naming system for the modes.)
Nevertheless, Zarlino revised his most popular treatise to include this new numbering starting on C, and it became the most widely disseminated discussion of modes throughout the seventeenth century. Zarlino was also perhaps the first theorist to suggest a kind of major/minor polarization of modes based on the quality of the third above the final, and his rationales in tuning and the connection to the hexachord for privileging what ultimately would be called a "C major scale" lived on, even if his numbering system wasn't always used.
The gradual decline of modal theory and the emergence of new "church key" systems with their related notions of transposition gradually allowed the creation of tonality and eventually the 24 major and minor keys. By the early 1700s, one can still see a kind of dual recognition of D Dorian and C major both as central primary scales for the new lists of keys. Dorian and Aeolian/natural minor continued to be alternative key signatures for "minor" scales in general well into the 18th century, though eventually our "natural minor" won out and D as central note faded completely from communal memory.
But C major, the scale with no sharps or flats, emerged victorious as the central scale/tonality/modality, a role it had first been cast in by Zarlino. French theorists who had been influenced by his numbering system, notably Rameau, would ultimately place the major scale on a supposed "natural" basis by expanding Zarlino's ratio arguments to new acoustical discoveries related to the harmonic series. Once valued only for its connection to the semitone below in Guido's day, the lowly C had gradually accumulated weight in its connections with the hexachord and clefs, only to be heralded as a new basis for a mode that ultimately took its place at the center of the Western musical system.
1The standard scholarly discussion of Zarlino's renumbering of the modes with the placement of C as the "first mode" can be found in Richard Crocker, "Perché Zarlino diede una nuova numerazione ai modi," Rivista Italiana di Musicologia 3 (1968): 48-58.
3Note that this pattern of tones and semitones could also occur on A, B, C, and D in the scale. Before letter names were adopted, these were alternative "final" notes for many chants, but later became thought of as transposed versions of the true final notes on D, E, F, and G.
4I've discussed the origin of the association of clefs with the notes F, C, and G in an answer here.
5Glarean is sometimes credited with "inventing" the major scale, but he did no such thing. Music had been written using a major scale for millennia prior to Glarean, even if it wasn't yet called a "major scale." And medieval musicians would have thought of such as scale as perfectly legitimate, even though from a chant perspective they'd have seen its proper foundational note on F (with a B♭) instead of on C.
6Two modes were given to each final note for authentic and plagal versions of each mode. These were originally introduced for chant melodies which had a high range that extended far above the final note (authentic) and those which tended to circle around the final note, going both above and somewhat below that central note (plagal). These distinctions were dropped when the modal system gradually gave way to the key systems for tonality in the 18th century.
7Zarlino's reasons are concisely summarized in Joel Lester, Between Modes and Keys (1989), pp. 9-12 and in Nejc Sukljan, "Praetorius Versus Zarlino: The Question of Modes," De musica disserenda 15:2 (2019): 105-124. For a discussion of Zarlino's renumbering in historical context, see Cristle Collins Judd, "Renaissance Modal Theory" in Thomas Christensen, The Cambridge History of Western Music Theory (2002), pp. 364-406.
8For a more detailed discussion of this process, see Randall Goldberg, "Where Nature and Art Adjoin: Investigations into the Zarlino-Galilei Dispute," Ph.D. diss. (Indiana University, 2011), pp. 59-62. Zarlino's incorporation of the tuning system into his arguments for renumbering the modes is discussed on pp. 209-216.
I feel this question deserves a shorter, more to the point answer:
Because when they decided to name the notes with letters, they took a minor scale and named the notes "naturally": A, B, C, D, E, F, G. This is what we know as the A minor scale.
Therefore the choice of names was accidental - it just happened that they considered a minor scale instead of a major one. Now if we want to use the same "natural" notes in a major scale, then we need to start with C.
If, however, we were to turn back time and influence the early notation to use a major scale as a basis, then they would name "A" the first note in the natural major scale, and then today we would talk about A major as the "standard" scale. But of course this "alternate" A would be the same frequency as "our reality" C.
"... the choice of names was accidental - it just happened that they considered a minor scale instead of a major one. Now if we want to use the same "natural" notes in a major scale, then we need to start with C."
I don't think it was accidental that first mode is A minor. Rather, it represents the music of the people that created music notation: Monks. An 'Aeolian-like' sound was the their preferred mode of music making. The notes of that "Aeoloian-like" sound would have been a minor scale. That is the sound they liked to sing- and the first note of it they named 'A'. Over the course of time there was a shift brought about by the development of the tempered scale, as well the development of craftsmen skilled in tuning instruments, which made it possible for Bach to write his music (dig The Well Tempered Clavier). Bach is really the beginning of modern music and, in a way, modern consciousness. When we ponder the key of C on the piano and wonder why it's not called A, it's because we don't perceive the bias we have for the major scale. It's become part of the foundation of Western consciousness. In my humble opinion...
Well, others have already mentioned that the A-G scale names precede Major as tonality and that the naming scheme is a bit arbitrary/historical.
The really curious thing is how C has become the octave starter, with B3 preceding C4 in scale (or, in other notation, b preceding c'). So obviously when a standard for octave notation was added to the note name system, C had already replaced A as the notation baseline.
That C has become "middle C" (and thus a prominent notation center in piano literature) is also a later development since the earlier collection of clefs was much more diverse than the current main system of violin clef and bass clef and there were several other notation systems for what amounted to organ notation before the current middle-C centric system that is now the basis for piano notation became the standard.
The theory that the Minor Scale starts with the letter A is plausible. However, has anyone thought of the fact that on a piano C is just the middle key (which we refer to as "Middle C") on the keyboard--half the notes are above it and half are below. It has nothing to do with Major or Minor key signatures.