We now think of Radio 3 as the music station, but when it was created in 1946 as the Third Programme music was only meant to take up one third of its output. Dramas, features, talks were just as crucial to its identity, and poetry especially was to be heard ‘three times a week and usually at a peak listening hour, not near midnight’ to quote a contemporary news bulletin from the Manchester Guardian. Last night the station began celebrating its 70th anniversary with a concert broadcast live from the Southbank Centre in London, where for the next fortnight there’s to be an ‘immersive’ Radio 3 experience designed to remind us of the station’s original intentions, with concerts, talks, live happenings. Tea dances with a swing band, yoga sessions accompanied by suitably relaxing classical music, poetry readings from a glass-fronted pop-up studio are planned. Anyone just passing along the riverbank is welcome to join in, yoga mats and leotards at the ready. Next Thursday, a new drama by Robin Brooks, The Present Experiment, will recreate (imaginatively) the station’s first couple of hours. It will be the first new play commissioned by the station for a while as it battles with cuts that have drastically reduced its ability to innovate and develop.

It’s difficult to justify spending on a station that attracts just 2.2 million listeners, compared with 15.2 million for Radio 2. That’s why these celebrations are so crucial, reminding us (and especially those who make decisions on funding) of why Radio 3 is such an essential aspect of the BBC, alongside Chris Evans, Today and The Archers. Tom Stoppard, Joe Orton, Harold Pinter all had their first plays produced by the station. It gave them their first experience of an audience, paid the bills (well, some of them, radio never being a very generous benefactor) and, most importantly, guaranteed them the confidence, the support, the motivation to continue. Something countless numbers of musicians have experienced as composers and performers for the station and especially its annual Proms season, which this year included 30 new works, several of them specially commissioned by Radio 3.

This week’s Sunday Feature: Vladimir Ashkenazy on Ansel Adams, was vintage Third Programme, using an unexpected connection between the Russian-born pianist and conductor and the creator of those haunting images of the American wilderness, especially the Yosemite national park, to explore ideas about music and photography. It shouldn’t have worked on air, since Adams is such a visual artist. But without being able to see the images we were given such accurate descriptions of the moonlight, the barren landscape and the stark rock faces that it was like seeing them in the mind.

Adams began life as a pianist and remained passionate about music as ‘the most expressive of the arts’. But by the time he was in his late twenties (he was born in 1902) he realised he would never truly make it as a concert pianist. At the same time he sold his first portfolio of photographs for $8,000. Although he believed then that photography could never ‘express the human soul’ in the way that performing Beethoven’s Moonlight Sonata might, Adams began to see himself as an artist of the darkroom, using his technical equipment almost like a musical instrument. The metronome that he used to measure out Bach or Beethoven was replaced by an electronic timekeeper, measuring out in seconds the necessary time for each exposure of light. Instead of creating photographs as mere records of what he had seen, Adams began using photography to express what he felt about what he had seen. The negative, taken on the spot at Half Dome, Mirror Lake or Hernandez, was the equivalent of the musical score, the notes, the beat, the composer’s intention. The print was the performance, the interpretation.

Ashkenazy only entered the frame at the end of Adams’s life, brought to California as a last gift to Adams from his children, to play the piano for him in a special concert. The Russian did not know Adams or his photographs, but surprisingly agreed to travel to California for the private concert. Sadly, Adams was too ill to attend but on meeting him Ashkenazy felt an instant rapport, as if they were in tune, the pianist and the photographer. He explains how you can see in the pictures the work of a musician, in the clarity, the use of light, the contrasts, ‘the heavens receding into a white pool’.

Earlier that afternoon, Words and Music (produced by Ellie Mant), perhaps Radio 3’s most innovative programme, focused on the sun, giving us a wonderfully visual selection of readings and music, from Ravel’s evocation of sunrise in Daphnis et Chloé to Coleridge’s poem, ‘A Sunset’ via Philip Glass, William Blake and Ted Hughes (the words read by Anne-Marie Duff and Greg Wise). It’s so refreshing, and daring, to be given no explanations, no notes, no introductions, so that all one can do is listen blind. But without those references, the connections emerge, meaning flows, thought concentrates and begins to make sense.