Apparently, one of the Radio 3 programmes we’re most likely to seek out and listen to online long after broadcast is…you guessed it, Choral Evensong. In other words, a weekly recitation in speech and song of words published in 1662 in a format that hasn’t changed since (if you discount the ecumenical variations that now fall under the same programme title, that is).

Two weeks ago, the Choral Evensong programme turned 90. Despite a blip during the 1970s, it has been broadcast from a church or chapel somewhere in Britain – sometimes beyond – every week since 1926. First and foremost the live Wednesday programme is an act of worship. But for those with little or no faith (which includes me), it’s something no less significant: a constant source of spiritual, communal, literary and musical sustenance. Tuning in to Choral Evensong – experiencing the heaving silence of the buildings from which it floats just as much as the words and music that eventually fill them – feels like touching base with one’s very existence.

Since I became a listener in 1999, the BBC has paused a few times to look back on its longest running outside broadcast, and the results have almost always proved surprising. The truth is, Choral Evensong has transformed almost beyond recognition even in the last 30 years, despite the constancy of the liturgy on which it is based. Performance practices have evolved, broadcasting technology has been updated, the language of music has been transformed, religious institutions have modernised and, most significantly, we as people are different. We hear these stylistic shifts acutely in the only broadcast on the planet that has used pretty much identical words and music since it was established.

Last week, Radio 3 continued to mark the programme’s 90th anniversary by broadcasting a service first aired in 1988 – more-or-less one third of the series’ life-span ago. The voice of the presiding clergyman, with his lightly rolled ‘R’s and air of whimsy, speaks of the days in which Church of England staff were invariably of a certain class. Prebendary WD Kennedy-Bell sounds quaint, reassuring, but also slightly unreal, certainly after the Scouse-accented priest who presided over a broadcast from Liverpool earlier this summer. Somewhere between those two broadcasts, women’s voices appeared on the airwaves, reciting the service’s opening sentences and singing the versicle O Lord, open thou our lips. Perhaps the conciliatory, hopeful tone of the contemporary Church of England means that heathens like me feel just as welcome and moved by what these men and women say.

The strength of those texts found in the Book of Common Prayer is proved by the extent to which new nuances have been unearthed with subsequent generations. Could he who composed such a resonant stanza as ‘we have erred and strayed from thy ways like lost sheep’ (perhaps a combination of Thomas Cranmer and Miles Coverdale) have known that in future centuries, the phrase would carry a certain lightness and gregariousness in contrast to the propulsive penitence with which it was probably conceived?

And as in any strand of repertoire, performance practice in church music has led to a process of dusting down and polishing off in the last half-century. Standards, to my ears at least, are as high as they have ever been in both performance and production (notwithstanding the series of technical glitches in 2012 that even made the tabloids). Choral Evensong isn’t a hierarchy; broadcasts come from Derby and Armagh as well as Wells and Oxford; each institution comes with its own changing micro-tradition. But recently, the programme’s fondness for Westminster Abbey and King’s College Cambridge has only served to demonstrate how the powerhouse music departments at cathedrals in Sheffield and Blackburn can deliver something no less beautiful and sometimes even more joyous.

I suspect many of those who seek out Choral Evensong do so for the psalms, which in the 1662 translations attributed to Coverdale are a literary treasure trove before music has even entered the picture. We can talk about how approaches to ‘composed’ church music have evolved – greater blend, more sophisticated attitudes to articulation, increased regard for the text, a generally more human and less mannered approach – but the recitation of the psalms to Anglican Chant doesn’t just sort the wheat from the chaff, it speaks volumes about a choir’s heartbeat, its soul.

That might be one way in which the programme is charting a sad tale of homogeny. There was a time when you could identify which choir was broadcasting from the psalms: Canterbury, Hereford and New College had rampantly idiosyncratic ways with this strange and wonderful gabbling hymnody. In the last 15 years or so, making the distinction has become a great deal harder.

Radio 3’s interface means that those who want to skip straight to the psalms can do so. Thus, perhaps the greatest change visited upon the Choral Evensong programme in the last 90 years has been the explosion in its reach and delivery via the web (a fact not lost on the raft of choirs that now webcast services under their own steam). Originally, the broadcast had the aura of eavesdropping; nowadays, clergy often welcome ‘those listening, wherever they may be’ – a tacit acknowledgment that they might just as well be listening on a Saturday night in the Jacuzzi a month after the event as be tuned-in live from the study on a Wednesday afternoon.

Evensong as a liturgical institution is far more than a radio show. But if the BBC’s Choral Evensong programme has become something more personal since the advent of the internet, then the poetry, music and spirituality embedded within the service have surely proved their depth and resilience as a result. The Corporation’s support for its 90-year-old enterprise in today’s climate feels almost miraculous. To be honest, I don’t know where I would be without it.