The lyrics for Mury were written in 1978 to the melody of the song L'Estaca by the Catalan singer Lluís Llach, which Kaczmarski heard on one of several Spanish records he borrowed from a friend in December of that year. The intention of Kaczmarski's lyrics was to examine how a song or poem can cease to become the 'property' of the author after it is 'stolen' by the masses, who may appropriate it for a particular cause even if it wasn't the author's intention in the first place. In this context, the song can be interpreted as supporting the Polish or Catalan struggle for independence, but also as a critique of certain aspects of mass social movements.
Despite its pessimistic conclusion and, ironically, despite Kaczmarski's intention to criticise social movements for sometimes 'stealing' the words of an artist, the song's message of struggling for independence against oppression meant that Mury quickly gained protest song status and it was soon accepted nationwide as the unofficial anthem of Solidarity. Its refrain later became the signal of the underground Radio Solidarity and the most popular part of the song, while its last pessimistic part was often left out. Kaczmarski came to see this phenomenon as both a misunderstanding of the song's meaning and a vindication of the point he was making when he wrote it. Nonetheless it remains one of his most popular songs. In 1987, after several years of severe repression by the communist regime in the People's Republic of Poland had managed to erode some of the support for Solidarity, and before the Polish Round Table Agreement of 1989, Kaczmarski expressed his disappointment with the disillusionment he saw in Polish society by writing 'Mury '87'. In this song, which is set to the same melody and which Kaczmarski referred to as an 'antonym' of 'Mury', he argues that instead of singing and hoping, people need to be taking action once again. In 2005, 'Mury' was performed by Jean Michel Jarre jointly with the Gdańsk University Choir and the Polish Baltic Philharmonic during the concert Przestrzeń Wolności on the occasion of the 25th anniversary of the formation of Solidarity.
