"When you're drowning," John Lennon told Rolling Stone in 1970, "you don't say, 'I would be incredibly pleased if someone would have the foresight to notice me drowning and come and help me.' You just scream."
"Don't Let Me Down" is Lennon's anguished scream to his lover, Yoko Ono. When he and the Beatles recorded the song during the Let It Be sessions in late January of 1969, Lennon asked Ringo Starr to hit the cymbal very hard at the beginning, to "give me the courage to come screaming in."
The Beatles were in the process of breaking apart when Lennon wrote the song. It was a dark time in my ways, and he was becoming more and more dependent upon Ono for personal and creative support. As Paul McCartney told writer Barry Miles in Many Years From Now:
It was a very tense period: John was with Yoko and had escalated to heroin and all the accompanying paranoias and he was putting himself out on a limb. I think that as much as it excited and amused him, at the same time it secretly terrified him. So 'Don't Let Me Down' was a genuine plea, 'Don't let me down, please, whatever you do. I'm out on this limb, I know I'm doing all this stuff, just don't let me down.' It was saying to Yoko, 'I'm really stepping out of line on this one. I'm really letting my vulnerability be seen, so you must not let me down.' I think it was a genuine cry for help.
You can get a strong sense of Lennon's anguish and vulnerability when you listen to the isolated vocal track above. And for the full arrangement, including Starr's cymbal-crash near the beginning and Billy Preston's brilliant electric piano playing, see below.