Detailed research made over the past few decades by various musicologists and lovers of music has tended to called in to question the iconic lives and official careers of the 'great' composers with which we are all familiar. To the point where it is possible to say with a high degree of certainty that the careers of many of the most iconic composers were hugely exaggerated. Owing their reputations, in fact, to various little known sources.
We are able to say with a high degree of certainty that W.A. Mozart (1756-1791) was not a 'musical genius'. That his musical talents were, in fact, rather average. But that his official life 'story' and even 'his music' was supplied to him throughout his career by numerous others whose names are often unknown today (though often published in Mozart’s name even after the time of his death) and that Mozart’s legendary status was being managed and invented at virtually every stage during his lifetime and beyond it by those who would eventually start to control the music industry of the 19th century. Who would start to control the editing and writing of textbooks on musical history itself, in fact.
The Mozart icon which dominates our western musical civilization was almost entirely manufactured. But this area of research, though highly controversial, may bring us to finally appreciate that great musical achievement in terms of composition is really the product of a society and always has been, rather than highly individualistic 'geniuses' of the kind we so often suppose.
It is not that documentary and musical evidence is lacking. It exists, in volumes. What is lacking is a desire within mainstream corporative and feudalistic musicology to dismantle its own icons, to re-examine its own simplistic versions of musical history and to be honest about its own prejudices and practices.