At BBC Proms from 10th August televised this evening.  National Youth Orchestra of Great Britain conducted by Edward Gardner.  Good use of short phrases and cross-rhythms – last movement clearly a passacaglia starting with really hushed double basses.  

Following link indicates the work is largely based on fragments of Poliosh folk songs local to Warsaw: http://www.laphil.com/philpedia/music/concerto-for-orchestra-witold-lutoslawski

On a technical point were the trombones flutter tonguing in some way or just muted?

Worth more intensive study in future! I have never played it.  

NYO performers on top form; excellent 3 solo violins with finger movement in the video that you would think was copied identically,  Leader has a very clean vertical finger action.