I think that 'Look at This' and 'Look a Little Closer,' though both sung by Joe Raposo, are two different songs. In Episode 514, which is (or once was) on YouTube, the former was used in a clip identifying individual parts of a boat, and then exposing the whole boat at the end (with kids saying 'It's a boat!'). This song was also used in one or two other clips as well - I think. On the other hand, the latter, which was used in other episodes around the same time (with items like tomatoes and tires), had a little softer, gentler melody to it, as opposed to the words 'Look - at - this,' being pounded out in the former. Moreover, in the latter, kids didn't say anything, but rather Joe finished the song with the line 'Did you guess what it is?...That's right!'
I hope the above explanation decently 'draws the line' between the two.
Actually, I stand partly corrected. In the newer version of 'Look a Little Closer,' the singer (I believe) is Bob McGrath and when he asks the question 'Can you guess what it is?', kids DO respond (unlike in the Raposo version). Just a somewhat 'minor' qualification!