Webster's Revised Unabridged Dictionary · 1913

Natural

Natural (?; 135) , adjective

[Old English naturel, French naturel, from Latin naturalis, from natura. See Nature.]

1.
Fixed or determined by nature; pertaining to the constitution of a thing; belonging to native character; according to nature; essential; characteristic; innate; not artificial, foreign, assumed, put on, or acquired; as, the natural growth of animals or plants; the natural motion of a gravitating body; natural strength or disposition; the natural heat of the body; natural color.
With strong natural sense, and rare force of will. — Macaulay
2.
Conformed to the order, laws, or actual facts, of nature; consonant to the methods of nature; according to the stated course of things, or in accordance with the laws which govern events, feelings, etc.; not exceptional or violent; legitimate; normal; regular; as, the natural consequence of crime; a natural death; anger is a natural response to insult.
What can be more natural than the circumstances in the behavior of those women who had lost their husbands on this fatal day? — Addison
3.
Having to do with existing system to things; dealing with, or derived from, the creation, or the world of matter and mind, as known by man; within the scope of human reason or experience; not supernatural; as, a natural law; natural science; history, theology.
I call that natural religion which men might know... by the mere principles of reason, improved by consideration and experience, without the help of revelation. — Bp. Wilkins
4.
Conformed to truth or reality
(a)
Springing from true sentiment; not artificial or exaggerated; -- said of action, delivery, etc.; as, a natural gesture, tone, etc.
(b)
Resembling the object imitated; true to nature; according to the life; -- said of anything copied or imitated; as, a portrait is natural.
5.
Having the character or sentiments properly belonging to one's position; not unnatural in feelings.
To leave his wife, to leave his babes,... He wants the natural touch. — Shakespeare
6.
Connected by the ties of consanguinity.
Related by birth rather than by adoption; as, one's natural mother.
Natural friends. — J. H. Newman
7.
Begotten without the sanction of law; born out of wedlock; illegitimate; bastard; as, a natural child.
8.
Of or pertaining to the lower or animal nature, as contrasted with the higher or moral powers, or that which is spiritual; being in a state of nature; unregenerate.
The natural man receiveth not the things of the Spirit of God. — 1 Cor. ii. 14
9.
(Mathematics) Belonging to, to be taken in, or referred to, some system, in which the base is 1; -- said of certain functions or numbers; as, natural numbers, those commencing at 1; natural sines, cosines, etc., those taken in arcs whose radii are 1.
10.
(a) (Music) Produced by natural organs, as those of the human throat, in distinction from instrumental music.
(b)
(Music) Of or pertaining to a key which has neither a flat nor a sharp for its signature, as the key of C major.
(c)
(Music) Applied to an air or modulation of harmony which moves by easy and smooth transitions, digressing but little from the original key.
(d)
(Music) Neither flat nor sharp; -- of a tone.
(e)
(Music) Changed to the pitch which is neither flat nor sharp, by appending the sign ♮; as, A natural. — Moore (Encyc. of Music)
11.
Existing in nature or created by the forces of nature, in contrast to production by man; not made, manufactured, or processed by humans; as, a natural ruby; a natural bridge; natural fibers; a deposit of natural calcium sulfate. Opposed to artificial, man-made, manufactured, processed and synthetic.
12.
Not processed or refined; in the same state as that existing in nature; as, natural wood; natural foods.
It should be borne in mind that the natural system of botany is natural only in the constitution of its genera, tribes, orders, etc., and in its grand divisions. — Gray

Model would be a preferable term, as less likely to mislead, the so-called artificial scales (scales represented by the use of flats and sharps) being equally natural with the so-called natural scale.

Natural (?; 135) , noun

1.
A native; an aboriginal. [Obsolete] — Sir W. Raleigh
2.
Natural gifts, impulses, etc. [Obsolete] — Fuller
3.
One born without the usual powers of reason or understanding; an idiot.
The minds of naturals. — Locke
4.
(Music) A character [♮] used to contradict, or to remove the effect of, a sharp or flat which has preceded it, and to restore the unaltered note.
5.
A person who has an innate talent that makes success in some specific endeavor, such as sports, much easier than for others; as, Pele was a natural in soccer.