This is an interesting conundrum - and to answer it, we must first look back at poetry as an art-form and it's early days.
Poetry throughout the medieval period was written, but mostly it was spoken as a form of 'entertainment', then with the introduction and with the industrial revolution and the ease of accessibility to books within the late 19th and early 20th centuries poetry transferred from the mouth to the pen - and from the stage to the page.
What is clear is that even today, there is still a divide between written poetry and performance/spoken word poetry. Why is this?
Above Kate Tempest performs at Glastonbury and has taken performance and spoken word poetry to new heights by doing so. However, if you look closely you can see that she has added music behind her words - is this not music?
Well, you could say yes, but actually if you watch carefully you will notice that the music is only a footnote next to her words - her verse shines through and hits home. Actually the music is the ideal accompaniment to her poetry.
The alternative, and still extremely important in the world of poetry is the 'Poetry Reading'; this can be seen to my right as Simon Armitage performs at Outspoken back in May.
Reading poetry is still 'performing' poetry - so there is still this element. The only difference being is the reason why it was written. There is poetry that is written for the page and there are also poetry that is predominantly written for the mic and performance.
This doesn't mean that poetry written for the page cannot be performed - far from it. What it does mean is that it might be slightly different in it's delivery.