The Heartz is associated with a pastoral topic and with emotion. As Rice puts it, "It is no accident that all three of the opera arias cited by Heartz contain the word core (also spelled cor). Eighteenth-century opera composers associated the sonic sweetness of the subdominant chord over a tonic pedal with the tender emotions of the human heart." (315)
The article has many examples, to which I will add three more. The trio of the last number in Beethoven's 12 menuets, WoO7, provides a simple instance of the Heartz figure. Note the ^5-^6-^5 with lower thirds and the descent ^5-^4-^3 (So-Fa-Mi) that follows. In this case, a cadence takes the line all the way down to ^1 for an unusual PAC to end the first phrase.
The contrasting middle in Mozart's theme for the first movement variations in K. 331 also uses the Heartz, but without the so-fa-mi. Although the many linear analyses of this piece show a descending line from ^5 down to ^2 in the half cadence, the voiceleading is tiered and Mozart repeats the Heartz figure a third lower (see ^3-^4-^3 below ^5). He maintains this design very clearly throughout all the variations except the last. (The example is from a facsimile of the first edition, downloaded from IMSLP.)
The strength of stereotyped patterns in the cadence apparently prevented musicians from reversing the direction of the so-fa-mi to la-ti-do. Schubert, however, does manage it nicely in D779n13, even adding some intensifying suspensions in an inner voice. He does change the underlying harmonies so that the entire pattern Heartz + la-ti-do runs above a cadence.
Reference: John A. Rice, "The Heartz: A Galant Schema from Corelli to Mozart." Music Theory Spectrum 36/2 (2014): 315-332.
