Joe Hisaishi — born Mamoru Fujisawa; the stage name is a Japanese reading of Quincy Jones, which tells you something about his sense of humour — scored Nausicaä in 1984 and has written the music for almost every Miyazaki feature since. That is one of the longest director–composer partnerships in cinema, comfortably longer than Spielberg and Williams had at the same point.
The image album comes first
Japanese animation has a practice with no exact Western equivalent: the image album, a record of music written from the concept art and early ideas, released before the film is finished and often before much of it is animated. Hisaishi wrote these for the Ghibli films, and themes from them worked backwards into the finished score.
The practical effect is that the music is not fitted to picture at the end of the process. It exists early enough to influence what gets drawn. If you want to hear what a Ghibli film sounded like before it looked like anything, the image albums are the place.
Minimalism under the melodies
Hisaishi came up as a minimalist — repeating cells, additive rhythm, the Reich and Glass lineage — and that training never left. Listen past the tune in something like the waltz from Howl's Moving Castle and you will find a small figure repeating with tiny variations while the harmony walks underneath it.
It is why the scores survive being played on solo piano. The melodies are simple enough to carry alone, and the machinery underneath them is regular enough to imply itself.
Silence as a choice
Count the unscored minutes in these films. Whole sequences of walking, cooking, cleaning and travelling run with nothing but foley and room tone. In Spirited Away the long train ride over water is nearly silent for a long stretch, and it is the emotional centre of the film.
This connects directly to the ma idea in the craft chapter. Music is a form of emphasis, and constant emphasis is the same as none. Ghibli's sound design treats a quiet room as information.
The films Hisaishi did not score
Takahata worked with other composers, and the difference is instructive. Grave of the Fireflies was scored by Michio Mamiya, whose sparse strings refuse any consolation. Only Yesterday leans on Hungarian and Romanian folk material that has nothing obvious to do with rural Yamagata and works anyway. The Tale of the Princess Kaguya, though, was Hisaishi's first score for Takahata, in 2013, near the end of both careers.
There are also the pop songs. Yumi Matsutoya's music sits at two hinge points of Kiki's Delivery Service. Whisper of the Heart is built around a Japanese version of Take Me Home, Country Roads, which lands strangely and wonderfully for an American viewer: a song about West Virginia, sung in a Tokyo suburb, about wanting to leave the suburbs.
A word on dubs and music
English dubs sometimes alter music placement, and older releases occasionally added score where the original had none. The 1998–2000s Disney-era dubs are largely faithful, but if a scene feels oddly wall-to-wall, check whether you are watching an English track. This is the single most common way a first-time viewer gets a subtly different film from the one that was made.