Going back to the writing of music notation format, it's much easier to write accurately and meaningfully for the rhythm section and the reeds of a jazz band or jazz big band. The subtleties that are achievable by trumpet, trombone, jazz violin or jazz vocalist are not so extreme. Interestingly enough, I was downloading a metronome from the Internet that would run on my tablet. I've already got a metronome, but it wouldn't give the correct variety of emphasis for 7/8 time. I was practising some Greek folk music that we were going to play for an event with my ceilidh band, and in some particularly complicated piece of music, I was getting thoroughly mixed up between the 7 beats being divided into 2, 2, 3 or 3, 3, 2 or 3, 2, 3 et cetera. This particular metronome was brilliant, in that each note could be programmed very easily to be a loud plonk, or a medium volume donk, or completely silent. The app was free, but there was a paid for version where you could have 2 (possibly 3?) dIfferent rhythms playing simultaneously, i.e. polyrhythms for practising jazz.
Where rhythm comes to the forefront, is in hot jazz where it can be more intense, exciting and complicated, faster and freer in rhythm and intonation and unpredictable, than sweet jazz rhythm or much of modern jazz.
However they are used, the majority of rhythms that characterise jazz associated with black American religious folk music. Despite this, a large number of the spirituals that have been transcribed and put into collections have little trace of these Afro-American rhythmic ingredients. A lot of the early jazz band played religious music, for religious ceremonies in church or weddings or funerals. Years ago I went to a local church, where have played many times with my string quartet to raise money for the church roof and heating, so I consider myself an honorary member of that church, to hear a jazz band playing music of the 1920s and before. A lot of it was religious music, and quite a lot of it fuelled music. It's jazz that one rarely hears these days, but it's jazz of great power and emotion, and is not often that you hear a 7 piece jazz band playing in a church of England church.
MORE ABOUT JAZZ RHYTHM.
So far I've been talking about jazz rhythm in terms of syncopation and pollyrhythm being an integral part of hot jazz. The consensus is that these rhythms are African in nature, but is the same sort of thing found in music from other countries, Europe, Central and South America, the Incas or North American Indian? Is there any trace of this in the Anglo Celtic dance music that was brought to America by white settlers, and still survives today in cowboy and hillbilly music, the jigs and reels hornpipes brought from Europe? Or has the music of these countries been integrated in some way into jazz? So, jazz and Brahms string quartets, in common with most music, are likely to use syncopations, so there's nothing so special about that. What is different in jazz is not so much that syncopation is used, but the sort of syncopation used and how it is used. The syncopation of Brahms string quartet is normally for a specific special effect, consciously used for its quality of standing out and emphasising. However in jazz, syncopations a basic structural ingredient that permeates the entire musical idiom, is to be found in virtually every part of the music. In this respect, the rhythms of jazz are more closely related to the rhythms of near Eastern and East Indian music than they are to European music.
Pollyrhythm is even more complex. Some claim the pollyrhythm is unique to jazz and doesn't exist in Western-style music. This isn't true however as pollyrhythm is used and has been used, but in limited specific uses, in Western European music. It doesn't permeate the music as it does with jazz. The polyrhythmic superposition of cycles of 2 over a fundamental rhythm of 3 units is common in European music, occurring in compositions written in triple time. Triple time is very rare in Afro-American music and in the early days was totally absent from jazz.
Of course, the popularity of American ragtime and jazz has spread internationally, and influenced all sorts of composers. Imitations of jazz styles have been included in many compositions, for example The Gully Will's Cakewalk from to Debussy's Petite Suite, which begins with a pollyrhythm that is taken from early ragtime. Stravinsky and others have taken jazz ideas and integrate them into their own music.
We've been talking about the influence of African music on the jazz that grew up in the southern states of America. Of course, other countries have had the same influence, such as Cuba, Haiti and Brazil. In America, the African music became mixed with a lot of Central European and western European influences, such as Jewish, Irish, Scottish, French, Italian and on and on. In countries of South America the African influences were mixed with Latin idioms, resulting in something different from jazz.
For many years Cuba had a marked influence on the world's popular music, prior to it becoming an outcast. The first form of Afro-American music to become popular worldwide, came in fact from the Habanera and Contradanca Criolla that became popular in Spain and eventually became integrated as part of Spanish folk music. In a very changed form, it was taken into Bizet's Carmen and Ravel's Rhapsody Espaniola.
African rhythms also shaped the tango, whose rhythms, thought originally to have been African, were similarly Latinised Argentina. I have a lot of arrangements for string quartet of tangos by a whole range of composers, with most complex probably being those composed by Piatzola, and used in the soundtracks of a number of films in the 1970s and 1980s. They are absolutely amazing piece of music, but like jazz, the emphasis is everything and the rhythms, though written down on paper, have to be felt rather than read and interpreted. Tangos, as hot jazz is also music of the emotions. The emotions are searingly extreme, rising to peaks of happiness and love plunging to the absolute depths of pain and hate and anger, all within a few bars of music. I always think of tangos as being somewhat akin to the very best of television adverts, which have to get their message over in 30 seconds, and a perfectly crafted the artistic and psychological and emotional sense, taking you through the full gamut of experiences in just a short time.
Other African influenced music of the rumba, the conga and the Samba. In some ways one can consider jazz, Brazilian music, Cuban music and so on as dialects of the same African parentage. Another dialect is the Calypso of Trinidad.
One thing is clear, that pollyrhythm dominates the musical language only where African influences enter into the music from the African population, usually if not always, because of the slave trade. So one could say that, through the evils of the slave trade, many musical artforms were born. Certainly not an excuse for what was done at that time, but at least something good has come out of it in the end. The United States of America is possibly the most interesting location, in that a large black population introduced their music into a country that had the influence of many other nationalities strongly represented. There were the cowboy songs of the south-west, the Anglo Celtic music of the barn dance bands and ceilidh bands in their jigs, reels, hornpipes and C shanties, there is a commercial popular music known as hillbilly music, which seldom contained any polyrhythmic structures. There is no pollyrhythm in the old cowboy song of Home on the Range, Green Grow the Lilacs, and so on and There's None Either in the Original Music the American Indians. So Pollyrhythm Can Truly Be Considered As the Distinguishing Mark of Jazz and the Evidence Points to the Fact That It Came Via the African-American Population.