Identification of uk birds by song

I find Merlin the most advanced and reliable, and it’s easy to use, but none are 100% reliable, so learning birdsong alongside using an app helps - the British Library ‘British Birdsounds’ CD/audiobook is a great resource

Hello James,   a lot of folk use  "MERLIN"  which is very popular and can be downloaded to your iPhone for free although bear in mind it is not 100% accurate and can throw the odd curve ball !!    it's probably the best ID of bird sounds I've come across,   other than that the best way to ID a bird by sight rather than by song is using the excellent Collins Bird Guide book which can be purchased in print or downloaded as an app (a little pricey but worth it)..