Swell it high and Sink it low. 
Hark! how the Treble and the Base
In wanton Fuges each other chase,
And swift Divisions run their Airy Race. 
Thro’ all the travers’d Scale they fly,
In winding Labyrinths of Harmony,
By turns They rise and fall, by Turns we live and die._

One might not unfitly compare to this difference of Instruments, the different Make and Constitution of Mens Bodies, with the Influence they have, and the Impression they make on their Minds, Passions and Actions.  From hence alone they may know much, how to direct their own proper Capacities, and how they are to suit each Person they are to use, to the most proper Employment.  As Mr. Pope Speaks of the Instruments of Musick.

     In a sadly pleasing Strain,
      Let the warbling Lute complain. 
      Let the loud Trumpet sound,
      Till the Roofs
      all around The shrill Echo’s rebound. 
    While in more lengthen’d Notes and slow,
    The deep, majestick, solemn Organs blow.

Harmony, in its most restrain’d Sense, is the apt and agreeable mixture of various Sounds.  Such a Composition of them as is fitted to please the Ear.  But every thing in a more extended Sense is harmonious, where there is a variety of Things dispos’d and mix’d in such apt and agreeable Manner.  Things may indeed be thrown together in a Crowd, without Order or Art.  And then every thing appears in Confusion, disagreeable and apt to disgust.  But absolute Uniformity will give little more Pleasure than meer Confusion.  To be ever harping on one String, though it be touch’d by the most Masterly Hand, will give little more Entertainment to the Ear, than the most confused and discordant variety of Sounds mingled by the Hand of a meer Bungler.  To have the Eye for ever fix’d on one beautiful Object, would be apt to abate the Satisfaction, at least in our present State.  Variety relieves and refreshes.  It is so in the natural World.  Hills and Valleys, Woods and Pasture, Seas and Shores, not only diversify the Prospect, but give much more Entertainment to the Eye, that can successively go from one to the other, than any of them could singly do.  And could we see into all the Conveniencies of things, how well they are fitted to each other, and the common Purposes of all, we shou’d find that the Diversity is as usefull as it is agreeable.

It is the same also with the World of Mankind.  If all had a like Turn or Cast of Mind, and all were bent upon one Business or way of Living, it would spoil much of the present Harmony of the World, and be a manifest Inconvenience to the Publick.  Perhaps one Part of Learning, or Method of Business, would be throughly cultivated and improved; but how many others must be neglected, or remain defective?  And it would create Jealousy and Uneasiness among themselves.  As Men are forc’d to justle in a Crowd.  For there would not be sufficient Scope for every one to exert and display himself, nor so much Room for many to excel, when all must do it in one Way.  Variety of Inclination and Capacity is an admirable Means of common Benefit.  It opens a wide Field for Service to Others, and gives great Advantage to Mens own Improvement.