Given the presentation of the letters on children's alphabet blocks, the suggestion is we're looking for a childish theme, and title Crib Notes furthers this notion by suggesting children's music of some kind (interpreting 'crib' as a baby's bed and 'notes' as the musical kind). The more obvious interpretation of the title as a succinct summary of an academic course or text also suggests we're looking at the concise version of some sort of list.
Given the large number of lines, it's expected then that with or without the above hints, one should be able to recognise some as the initiailisations of the first lines of nursery rhymes. For instance, the first line SAS_S is such a conversion of the rhyme Sing a Song of Sixpence, whose first line is itself "Sing a song of sixpence". Clearly then the missing letter should be O for 'of'.
The lines then are as follows, with the missing letters highlighted in bold:
The missing letters spell out Old MacDonald had a farm, the first line of another well-known nursery rhyme. The ellipsis at the end of the puzzle suggests we should finish off the first line, giving E-I-E-I-O as our final answer to a puzzle concerned with expressing nursery rhymes as nonsensical strings of letters.
|The answer is: eieio|