It's a little-known fact that the English invented music. Not all of music -- but the music that might be expected to sound normal to `Western' ears. And not invented -- more like set in place a complex chain of events that eventually left us with Stravinsky and Lady Gaga.
To fully understand this exciting proposition, we need to know what European music was like a very, very long time ago -- in fact, in the Middle Ages. In the monasteries and cathedrals across Europe, since the 6th century, Plainsong was sung: line after line of unadorned melody; fairly beautiful, but I wouldn't be able to stand a whole CD's worth of it. (It is best relegated -- as it has been by now -- to occasional incipits and intonations to movements of Renaissance polyphony, and sometimes a Psalm, if someone hasn't bothered to photocopy the proper chant in time.) Then, sometime in the 9th century (thanks Wikipedia), a few ambitious monks remembered that the Ancient Greeks had discovered that the intervals of a fourth and a fifth sound "pretty neat" (a direct translation from Pythagoras, no doubt), and tried out singing, in parallel to the main plainsong chant, a version transposed up or down by one of these intervals, no doubt embellished here and there as appropriate (this style is known as 'organum').
And so, all the way into the 12th century, we have a Frenchman, Léonin, whose compositions are effectively written out versions of slightly complex organum experiments -- all for just two vocal lines, though we can of course speculate about additional ornamentation that they may have tried. The venerable contemporary commentator on medieval music, known to us only as "Anonymous IV", tells us that a bit later on (the early 13th century) Léonin's work was surpassed by a certain Pérotin, who extended organum into works consisting of three and even four vocal lines -- he had lots of fun constructing complex rhythmic altercations over stretched-out plainsong lines, all fundamentally in the organum style. The situation that music was in now is called the "Ars antiqua", or Ancient Art. Towards the middle of the 14th century, the narrative is picked up by another Frenchman, Guillaume de Machaut, who composed complicated, four-part music, in a variety of styles -- a Roman Catholic mass, various secular songs (ballads, rondeaux and motets), and the like. The interesting thing is, to modern ears, even this mid-to-late 14th century end-of-the-Middle-Ages music sounds really, really weird. The chord progressions make no sense: Machaut hovers around strange minor chords, and it is quite clear that anything that sounds remotely normal is just a chance arrangement of chords in a pattern which seems familiar. Of course, we may judge this music to be "nice", in the same way that we may appreciate an atonal 20th century composition that we cannot harmonically understand, but which can still sound somewhat attractive to our ears.
Machaut was writing in the 1360s, yet if we listen to music by the celebrated Palestrina from, say, the 1570s -- slap bang in the middle of Renaissance Italy -- the music sounds sensible, harmonic, and basically sane. It is easy to see a gradual transition from Palestrina to Monteverdi, to Bach and the Baroque, Mozart and the Classical, Schumann and the Romantic to the wonderful explosion of musical styles that took place in the 20th century (such as Stravinsky! and Lady Gaga!). All the tonal music from Palestrina through to, well, perhaps Wagner, used the same basic set of major and minor scales and chords -- yes, music was supposedly "modal" in the Renaissance (it wasn't really) -- but all this music is appreciated on the merits of the basic chord changes from tonic to dominant and back again (and similar tuneful progressions). And the only reason we got atonal 20th century in the way we did was as a particularly extreme development of (or maybe reaction to) this basic tonal style of music.
So how on earth did we get from the confusing mess of Machaut to the harmonic beauty of Palestrina and beyond? Thusly: around the end of the 14th century, an Englishman named John Dunstaple (some insist on calling him Dunstable; the sources disagree) realised how to make music nice. Before him, people such as Machaut had been building chords out of fourths, fifths and thirds rather haphazardly -- avoiding semitone and tone clashes, but basically filling in their vocal lines according to the general idea that fourths and fifths sound OK, and thirds are also quite alright sometimes. Dunstaple realised that if you take a traditional Medieval dyad (like a chord, but with only two notes) of a simple, bare, fifth, as had been used in organum for centuries, and combine it with a an interval of a third, you get a pleasant-sounding triad, one on each degree of whatever scale you happen to be using, which can be happy (major) or sad (minor), and will generally make your music feel more harmonic and fulfilling. But not only this -- for surely, you protest, even Léonin would have noticed that these simple "triads" exist -- Dunstaple discovered that one can produce arbitrarily long sequences of these triads, according to some moderately simple rules, in a way that sounds coherent and sensible. Dunstaple was very inventive with these new-found things to do with chords -- for example, his music contain hints even at the profoundly jazzy English cadence, beloved by choristers worldwide. The chord progressions that he thought up formed the basis of the music of the Renaissance, although the momentum quickly shifted to the continent, with the result that Dunstaple is often forgotten.
The early Renaissance masters, such as Dufay (born around 1397) and Binchois (around 1400) owed their success to the great advancements in musical knowledge brought about by Dunstaple and his English contemporaries (Lionel Power was another). People soon noticed this change -- from a 1442 poem by Martin le Franc discussing contemporary composers such as Dufay:
"Car ilz ont nouvelle pratique
De faire frisque concordance
En haute et en basse musique
En fainte en pause et en nuance
Et ont prins de la contenance
Angloise et ensuy Dunstable
Pour quoy merveilleuse plainsance
Rend leur chant joyeaux et notable."
"For they have a new method
Of making fresh harmony
In music both high and low
In artifice and interruption and nuance
And have adopted the English
Habit and followed Dunstable
Because of which wonderful delight
Makes their song joyful and remarkable."
And from Dufay there followed Josquin (born around 1450), who led directly to the greats of the later Renaissance -- Palestrina, Victoria and Lassus (et al.). And having accomplished all this, Western music had pretty much got it set.