bird song

hi im new here so please be patient with me ,lol, i have a small garden aprox 35ft square ,with a 1,000ltr pond and a 750ltr pond connected by a stream (i will post pic,s soon)  we get hundreds of birds of all types including what i thaut to be a giant robin , it turned out to be a bullfinch and his partner? also a small greyish bird with a pale blue underside who runs up and down my greenhouse catching insects? spiders? but a few nights ago i was sitting (having a couple of cans) and it was getting dark, i was waching for bats ,which we have a lot of round here, when i heard a bird in my neibours tree, all the regular birds had quit singing, this one had the most haunting song i have ever heard, it was like a cross beween pan pipes and a softly played flute, it sang for about 3/4 of an hour , i just wish i had something to record it,  this went on for three nights, (even my 5 yearold grandson enjoyed it?   i was told it would be a nightinggale but when i checked online for its song its nothing like the one i heard , far to squawky, and loud, so if anyone could tell me what it could be i would be greatfull, ps i also have a blackbird nesting in my shed?? she gets in through a gap in the bottom of the door, the has 3 chicks and two unhached eggs as yet, shes not botherd about me and jackie pottering about in there?? yours hopefully, terry,