Ah; when people say "song", that usually means to me a tune with words; I gather that "song" is often used to mean "tune" in some places, though.  Ossian was a Scottish band, active originally in the '70s and 80s; Ae Fond Kiss, the tune of which I suspect you would recognise straight away if you heard it (it's very slow, and ends on an unresolved note as I described), was on their first album, Ossian (Springthyme SPR 1004, 1977); it's available now on CD, and the band itself is back together and working again.  Presumably, then, it was an instrumental version of the melody that you heard?  The tune, in various forms, is as I said used for a number of songs in Scotland and Ireland, for example:

Ae Fond Kiss  The tune given with the file is the one Burns set it to, Rory Dall's Port, which, though it seems to be related, is not quite the one that we're talking about.

Donal Og  Text; one of a number of translations into English.

Donal Og  A midi of one version of the tune.

Hi [H]Oro 'S Na Horo Eile  Text only, but it goes with the tune I linked to in my last message.

All this doesn't tell you where you heard the thing, of course, but it may help someone else to put their finger on a film, or whatever.  And if not; well, at least you know things you didn't know before!

Malcolm