Sir Paul McCartney thinks songwriting is like ''talking to a psychiatrist''.

The Beatles legend still gets a ''buzz'' when he writes a new track and finds it incredibly useful to be able to pour his troubles out into new lyrics.

He said: ''I still get the same buzz from songwriting. There's a black hole. There's nothing there. And you start going da-da dum-di-dum-di, and there's suddenly a song. Sometimes it's like talking to a psychiatrist, because you've got your troubles out. You feel satisfied.''

The 77-year-old musician also finds it easier to reveal his ''awkward truths'' and ''innermost thoughts'' in his lyrics than to speak about them directly.

He admitted: ''In private life, I don't want people to know my innermost thoughts. A song: that's the place for them.

''Like in 'Here Today', when I'm saying to John [Lennon], 'I love you.' I couldn't have said that really to him unless we were extremely drunk.

''But you find you can put these emotions and these deeper truths and sometimes awkward truths in a song, whereas it'd sound daft if you'd just said it. That's one of the things I like about songs.''

While Paul likes to jot down ideas for songs as he's going about everyday life, he admitted there is a ''danger'' to the approach as it's left him with ''millions'' of snippets of music that he's never finished.

Speaking on BBC Sounds' 'Mastertapes Guide to Writing the Perfect Song', he said: ''Having recording devices in your pocket is such a danger. If I get an idea, I'll grab the cassette, hum a bit, think, 'I'll finish that later.'

''I've got millions of cassettes, full of snippets I've hummed. Where did I want that one to go? You say you'll finish it later but you never do.''