You CAN say something about melody . . . YOU can say something about melody!
Melodies combine pitches and rhythms.
Types of melodic motion
Does it move in generally stepwise (conjunct) motion, or does it move with larger intervals or skips (disjunct motion)? Examples of stepwise motion would be start of the Christmas carol "Joy to the World" or the Beatles’ song "Norwegian Wood." An example of disjunct motion is the "Star-Spangled Banner." Most melodies combine stepwise motion with small skips. The melody for "Somewhere Over the Rainbow" starts with a prominent leap. The Robert Johnson "Cross Road Blues" (on textbook CD) features a prominent falling large interval. Features like this are worth noticing and commenting on. Does the song you are analyzing have a big leap in the melody? Some melodies repeat the same note or a couple of notes a lot, with just a few departures. Are the departures significant?
Most melodies that move in a disjunct manner necessarily have a large range (for example, the "Star-Spangled Banner"). Some melodies can have a narrow range. A melody with a range of about an octave would be fairly normal. Something with a range of only four or five steps would be considered a small or narrow range. Some rock songs will confine the singer to just two pitches a step away. (Examples like this would necessarily have a lot of repeated notes.) This is a very small range, and would be well worth commenting on. A range that is larger than an octave would also be worth commenting on.
Articulation describes the degree of connection between notes. An example of notes in a smooth and connected melodic line would be "Norwegian Wood." The opening of Mozart's Eine Kleine Nachtmusik (on textbook CD) is very detached and separated. To introduce some Italian terms, notes that are smooth and connected are legato; notes that are separated are staccato.
Melodies are rarely streams of constantly new pitches and ever changing rhythms. Many melodies repeat rhythms (often with different pitches). Many melodies repeat groups of pitches and rhythms. These segments are combined into larger and larger groups called phrases. (Example: Vivaldi's Spring Violin Concerto; on textbook CD.) The melody to "Norwegian Wood" repeats a general shape or contour several times. When a specific melodic shape is combined with a consistent rhythm, that can be considered a motif. The most famous examples of motific construction are Beethoven's 5th Symphony and Mozart's Symphony No. 40 in G minor, but motific construction is a very general technique that permeates a great deal of music. For example, part of the chorus of Nirvana's "Smells like Teen Spirit" (the section that includes the lyrics “Here we are now . . .”) uses a repeated rhythmic motif with the same falling pitch contour. If a melodic idea or motif is repeated unchanged, it is called a riff (in jazz and rock).
The book combines several ideas into one general idea of "tunefulness." One way of thinking about "tunefulness" is the degree of psychological unity or compactness that a melody may have. The Charlie Parker tune "Mohawk" (on textbook CD) is a fascinating melodic construction, but it is difficult to grasp all its details in one hearing, so it is an example of a melody that is not “tuneful.” Melodies that are built up of small simple units that feature conjoined motion and a strong sense of closure usually are considered to be "tuneful." As the book takes pains to point out, this is not a judgment about whether the melody is good or bad. In your analysis project, you can use “tunefulness” as a descriptive term, but it would be even better to explain why you consider it to be tuneful.
One quality of a melody is its degree of closure. Does it have a clear end? This usually can be heard in melodies that have a clear phrase structure. The first phrase is obviously the opening phrase. There may be continuing phrases in the middle, and there is a clear closing phrase. Some melodies don't have such tidy finishes. For example, the melody that is the fugue subject of Bach's “Little Fugue in G Minor” has a very memorable opening hook, but nothing gives it a sense of completion. That is all by design, of course. A clear sense of closure is a characteristic of music in the Classical Era and of most popular music. Romantic composers, particularly Wagner, sought after the unobtainable ideal of "endless melody." What is the emotional feel that you get from a melody with a clear sense of closure as compared to a melody that has a less definite ending?