Piano, diminuendo(Italian) Softly, with gradually diminishing volume. These are common musical terms.
A tempo(Italian) at the original tempo (i.e. speed). This musical direction is generally used after a change of tempo (e.g. accelerando) to indicate that the performer should resume the original tempo. Here, however, there has been no change of tempo — in fact, no tempo has been specified.
Stringendo(Italian) with gradually increasing intensity. This musical direction is often loosely equated with accelerando (gradually getting faster), but its meaning is broader. While it is true that the tempo is usually increased, so too are the volume and intensity of expression. Here, Stephen is becoming more and more excited.
