A  rare Van Morrison recording was released out of the blue on iTunes on Wednesday – and promptly disappeared, apparently as little as an hour later.

The recording is a legendary one, made in advance of the release of Astral Weeks – widely considered to be one of the seminal recordings of the latter half of the 20th Century. Its existence has long been rumoured, but even the most diligent Van-ologists had failed to get a hold of it. Now, however, that spell has been broken, by Van the Man himself.

The live Van Morrison recording was done by Peter Wolf, who is most famous as the lead singer with the J. Geils band – but who was also a DJ with a Boston radio station at the time and was friendly with Van. The gig took place in The Catacombs, a much loved Boston venue. And the recording is said to contain at least one Van Morrison song – in the form of 'Train’ – and perhaps more, which have never otherwise been released.

The recording, when it appeared on iTunes was titled Live In Boston 1968. There was no cover art as such. But even more unusual was the decision to make it available and then to remove it. As a result, a small number of Van Morrison fans will have paid for and downloaded it – but a much greater pent-up demand has potentially  been created. The album was available in the UK, but not in the US – with a number of Vans’ Stateside fans trying to find ways around the digital wall to secure the precious music. It is not clear how many succeeded.

There has been immediate speculation that the recordings might now be made available as part of a special Astral Weeks box set. As the new box set of Bob Dylan’s Blood On The Tracks confirms, there is a huge amount of interest, among knowledgeable fans, in additional material to do with classic albums.

One theory being advanced to explain the now-you-see-it, now-you-don’t release strategy – to which there is a hint of espionage – has to do with copyright. In effect, this hypothesis runs, by releasing the album even for a short period of time, Van Morrison has secured the copyright on the material – and in particular on the previously unreleased tracks like ‘Train’ – which otherwise might have transferred into the public domain because of the 50 year rule.

“I’ve always heard that this was an extraordinary show,” one music industry insider told Hot Press. “It is in that legendary category, and it may well have been the gig at which the producer Lewis Merenstein saw Van perform the songs that would ultimately become Astral Weeks. So there are all sorts of reasons why it is seen as a recording that is of real, enduring historic interest. The fact that it may well be Van Morrison in full flow playing songs live that have resonated across the decades since then makes it potentially irresistible!"