There was a time when a spin along the radio dial was a voyage of discovery, when the crackle and whine of the medium and long waves between stations was an overture to finding another musical world. Rock, classical, jazz, folk, Euro-pop, blues, punk, Latin American, world music – it all used to lurk on there, especially at night when the broadcasters used to come in from all over Europe.

Generations of us without the means to experiment by buying records found a musical education that way, stumbling for free across stuff we'd never heard before, gradually broadening our horizons and homing in on the genres that spoke to us most persuasively. And that was why, when digital radio came along, I, and I suspect a lot of other people, raised a cheer. Not because it was a hi-tech a return to the good old days, but because it was potentially a new golden age of radio and musical discovery.

Dozens of radio stations, they said. A place for all tastes. The chance to sample all sorts of music – and in CD quality, without the whizz-bang distraction of interference caused by everything from planes going over to the washing machine starting its spin cycle.

Sadly, it's all proved too good to be true. The promise of access to new musical worlds can't compete with the bottom line. Commercial radio giant Gcap says it can't make two of its specialist stations – theJazz and Planet Rock – turn a profit, so they are being axed. Both had hundreds of thousands of listeners, but weren't bringing in the advertising revenue they needed. And even more worrying, Gcap says it's gloomy about the prospects for the whole concept of digital radio, even the stations that concentrate on top 40 playlists that get mass audiences and bring the money in.

theJazz had become quite a favourite of mine, and I regret its imminent demise. There will be many who hold Planet Rock in similar affection. That, though, isn't really the point. It's not so much that the loss of either leaves a little hole in individual lives, it's more a matter of the arts and cultural scene for everybody being diminished in its variety and choice.

Where now do the curious turn to hear something they like the idea of, and would like to sample? theJazz and Planet Rock won't be the last specialist music stations to shut down if Gcap is correct. The commercial stations are wedded inextricably to the top 40, and though BBC Radio 2 makes valiant efforts to keep the flag flying for wider musical worlds, the specialist genres are inevitably boxed in to an hour or so once a week.

So a fond farewell to theJazz. It's been fun. But sadder than that, much sadder, a regretful farewell to the chance of new voyages of musical discovery across a whole spectrum of genres. We're all the poorer for that.