The 5th Dimension's "(Last Night) I Didn't Get to Sleep at All" is a very rewarding song for a singer who can put it over well. The melody gives Marilyn McCoo a challenge: she has to keep the low notes on those abrupt downswings "up in the air" as it were. Vocalists have a natural urge to go flat when they're unsure of the pitch, when the musical gravity of the song is pulling them down and they lose control of their ability to resist that force. "Last Night" succeeds because of this Sisyphean tension (and because McCoo's such a great singer) -- the lines go up up up, sometimes allowing for breathtaking octave leaps, and as listeners we're rooting for them to make it up the mountain, but right until the end they keep rolling back down, brushing themselves off, trying again. The reward is that the high notes are fabulously singerly -- there's a built-in momentum in the shape of the ascending phrases that makes McCoo sound flashy even though she's not doing anything technically dazzling (this has to do with the lyrics as much as the melody; "sleep at all" comes out as "slee - PAT - all," and the aspirated "p" sound gives a little fuel to the "at" syllable, makes the note come out clear and forceful; in the chorus, the octave-jumping "last night" has a slight connecting swoop where the openness of the "a" vowel in "last" gives the "i" in "night" a bit of a push, puts some wind in its sails). Pop songwriters just aren't this conscientious anymore. Hats off to Tony Macaulay!