Because composers tend to use the same patterns over and over again, it is possible for a song to be contained in another song. So far we have found only one example of a tune that is contained entirely in other tunes, and even that’s a bit of a cheat. That song is an African-American slave chant called “I Want to Go Home,” collected in the 1860s.
Here is the tune:

As a chant, the notes were written down by the song collector as whole notes, but as in all chants one or more words would be sung to each note. We don’t include chants that are written entirely as whole notes because they don’t include individual notes for each word in the lyrics, and are therefore not proper melodies. We cite this chant here as an interesting example of how song phrases are included in other songs.
Keeping in mind that, for our purposes, what matters with respect to finding this pattern is that all the notes have the same duration. That means that each duration ratio between any two consecutive notes has a value of “one.” With that reminder, we observe that there are over 50 tunes containing the chant, “I Want to Go Home” in its entirety. Some examples in chronological order:
Songs Containing Entire African-American Chant
Year Name 1684 Faronells Division on a Ground, var #7 1694 Jig #175 in Henry Atkinson Manuscript; also, Pretty, Pretty Miss, Let’s Talk Together 1701 Ladder Dance Tune No. 116 1737 Giga from Sonata No. 1, Il pastor fido, Op. 13, RV 54, mvmd 4 1741 Les satirs Punie, giga 1748 Marble Hall 1750 Gillian the Drover 1751 Show Me the Way to Oxford 1754 Wiell a’ to Kelso Go 1776 Jackson’s Morning Brush 1800 Toutouic 1804 Mallowne’s Jigg with Variations 1840 Toby Peyton’s Plangsty 1903 March of the Toys from Babes in Toyland 1910 In Sorrow I Wandered 1906 Pan et les Bergers (Shepherds), 3rd strain, Op. 15, La Flute de Pan 1932 Masquerade 1955 Day-o (The Banana Boat Song, var I)
1956 Les Folies d’Espagne (var 4)
Unless you are a music aficionado, you will not have heard of most of these, but one of the oldest tunes to contain the “I Want to Go Home” pattern is Jig #175 in the 1694 Henry Atkinson Manuscript.

You can compare the encircled notes with those of I Want to Go Home to see they are identical in change of pitch and, because each note has the same duration (quarter notes in the jig), the duration ratios are all “one.”

You might be curious how this chant works into the popular Caribbean song, Day-O, so here’s the portion of that tune with this exact progression of notes. Again the encircled notes can be shown to be identical in pitch change and duration ratio to the chant’s, but here the tune employs them as eighth note triplets.
So far, songs contained in other songs is just a curiosity. We will see if it emerges as more than that as we enter more melodies.