I don't know, because no-one has defined a standard by which "worst" can be assessed. Unless someone can define what is meant by "the worst piece of music", then no-one can meaningfully nominate a possible candidate. If it is possible to write a worse piece than any previously composed, how would we recognise it as such?
Thankfully the rich diversity of criteria and example by which bad music may descend to the depths of 'worst' is so broad, that there is scope for the truly talentless to keep putting out execrable drivel for many centuries to come ;)
