The one on the left is Starry Night (1889) by Vincent Van Gogh. On the right shows a girl searching a soldier by graffiti artist Bansky (2007).
Many would perceive Van Gogh's paintings as high culture, after well over a century his work is still viewed as high culture. The work of Bansky and other graffiti artists is more recent and perhaps classed as low culture. However Van Gogh has become more mainstream and is a part of mass culture today, practically everyone has heard of Van Gogh and Starry Night; its even entered popular culture and is the basis of the Don McLean song 'Starry, Starry Night', while Bansky is highly rated as an artist for his art but also what his art expresses. Many graffiti artists, like Bansky, have successfully had their art enter galleries alongside the works of such artists as Van Gogh.
This is why I think Adorno and Horkheimer's thoughts are inaccurate when describing culture; they believe mass culture to be wrong and false, but I think that mass culture will benefit society and enrich both high and low culture, and maybe even allow both groups to cross like in the images shown above.
Also, the idea that Adorno and Horkheimer believe that:
"Movies and radio need no longer pretend to be art",
is not true in my opinion. I don't think that movies and radio have ever pretended to be art, they are forms of art. They express an idealogy that allows people to form their own views and opinion which they can also express through various types of media, especially today with the invention of the internet and YouTube.
Adorno and Horkheimer's views that 'culture has been industrialised' isn't entirely wrong; the industrial revolution has drastically changed the world and spawned capitalism, but why should that be a bad thing? I feel that it only heightens the ways in which people can express their ideas, their beliefs through various forms of media that were not around prior to the industrial revolution such as radio, television, film and the internet. This, I believe, intensifies and fuels the hunger people have to learn more about their society and the world they live in and to spread culture to the masses.