Interesting idea. I can't at first glance see anything obvious though: my line seems to be just a normal telegraph line that travels to the pole across the road, and it looks like it goes underground after that (I can't see a line leading to another nearby pole).

There is one other little titbit I forgot to mention earlier, in case that helps prove (or disprove) your theory: I only hear music when the phone is plugged directly in to the master/test socket, not through the micro filter.

Also, re. MrSaffron's suggestion earlier, unfortunately I can't identify the the radio station (assuming it is one) at all. It's Indian music and so far all I hear is music, no talk that might give me a hint.

I did explain that in an earlier draft, and that the OP and many readers may not know or if they did may have forgotten, but it began to read like a treatise .

I cut it to the essential. My point was that the CS staff and the engineer, who may or may not have been from Openreach and in any case could be a recent recruit, could have been getting confused. For instance, following "Occasionally the ADSL drops too, perhaps for a few minutes, perhaps for an hour, which isn't ideal", we have:-

In reply to a post by Be3G:

Last time my line dropped for a significant period of time I reported it to A&A as a PSTN fault; an Openreach engineer came round but couldn't find anything wrong (though acknowledged the existence of music through the corded phone) so nothing changed.

That almost certainly means a phone engineer was sent, not a broadband engineer. When the problem was the broadband had dropped for a significant time.

Then we have:-

In reply to a post by Be3G:

I've already done the testing through the test socket etc., and indeed reported it to A&A as a PSTN fault as I have my phone line through them too.

Uh uh!

We don't really know what the OP said to CS, but the odds (in my opinion) are that a phone/voice fault has been reported to Openreach. The wrong sort of engineer was sent. Would they be bothered about music on a line that didn't have a phone service, given that the engineer could well know nothing at all about the effect that would have on broadband?

Zarjaz's post was relevant, as it tends to annul my theory any such lines are terminated on a service that plays music, as at the moment Openreach and particularly BT Wholesale that I think the OP is on (I think their ADSLx service is only on BTW not TalkTalk but I could be wrong) do not generally do a line-only connection for broadband.

In reply to a post by Be3G:

There is one other little titbit I forgot to mention earlier, in case that helps prove (or disprove) your theory: I only hear music when the phone is plugged directly in to the master/test socket, not through the micro filter.

That is important information. The micro-filter passes everything on the line through to the modem. It removes all signals in the broadband frequency range from the phone port.

That is to make it possible to converse on the phone. The modem just looks for the expected broadband frequency range and ignores the rest.

However, although it is important, it is confusing in itself. As music is in the audible range so should get through the filter anyway.

In reply to a post by Be3G:

Yes, for the avoidance of any doubt that is what I have, albeit with an added incoming calls facility that A&A were offering as a free but optional extra when I signed up with them.

You've got an intriguing problem, I wonder if the music is possibly an incoming calls test facility that is triggered by your particular corded phone when doing a quiet line test (?) via the test socket. The music is not heard when the phone is connected via a filter and perhaps due to the filtering of the frequencies a test is not triggered.

Just a wild guess

It was indeed a voice fault that was reported, and the engineer who visited was tackling the problem as such. That is generally the best approach to take though, is it not? I've been using ADSL now for fifteen years with all manner of issues at my previous abode and it was always the case that if there was a broadband fault which coincided with a phone/voice problem too, it was best to raise a PSTN fault first as that would in all likelihood fix the ADSL problem too.

Bear in mind that I do have a line with phone service. I can receive calls and make outgoing non-chargeable calls � it's really a normal phone line just with outgoing chargeable calls barred.

(And yep, I'm on BTw.)

Also, whilst not entirely relevant since you have an incoming calls and outgoing non-chargeable calls service, A&A say this:

"No telephone service is provided on this copper pair, it is purely for broadband use.

Whilst there is no telephone service as such, the pair does have some audio when connected to a telephone - this is purely to stop any engineers thinking the pair is unused and taking it for another installation or fault repair. It also allows a quiet line test so one can hear crackles or interference that may be the cause of a fault. As such we still expect customers to have a telephone handset available for fault repair and diagnostics." - https://www.aaisp.net.uk/broadband-phoneline.html

They don't say what the audio is though...maybe normally just a dial tone?

Edited by 4M2 (Sun 15-Oct-17 18:29:54)

So wild that I'll discount it

Yep OCB dial tone I expect.

I feel the post by Zarjaz and the fact that the phone does not produce music with an ADSL filter in place are very relevant here.
The ADSL signals are in the same frequency bands as LW and MW radio signals, which are a significant source of interference with ADSL.
If, as suggested, the overhead line were picking up a radio station it is possible that OP's phone could be rectifying that RF signal and producing the audio that's being heard. The micro-filter is there to remove all but audio frequencies from the phone, it doesn't effect the ADSL at all.
A different phone might not behave in the same way but it seems clear that the offending signal is on the line at radio frequencies rather than audio. That must be why there is an ADSL issue.
The OP needs to ensure the fault is reported as an ADSL one rather than a phone fault so that he gets the right engineer who knows how to deal with the issue

Thanks for your input MatHal, sorry it's taken me a few days to reply.

Inspired by that post I've done some more testing. I have a couple of spare microfilters but also a simple telephone socket doubler, so I thought I'd see what happens with either of those, in case the situation was that inserting anything between the corded phone and the NTE5 killed the music, not specifically a filter. But I can confirm that your and Zarjaz's theories seem to hold up, because I don't hear music through any of the filters but I do hear it when the doubler is in place instead.

With a bit of luck, I also happened to �tune in� when there was a news broadcast rather than music, so I listened very very carefully and after a few minutes I heard the radio station being announced: Punjab Radio, which is on 1584kHz in London. This fits neatly within the ~2MHz maximum frequency of ADSL2+.

So, with that in mind, does it look like there's now no point to me purchasing another corded phone to test with, because it might or might not let me hear the radio station so won't be conclusive either way?