Grammatical morphemes are used to modulate word meanings and to link words in constructions. They consist of inflections, usually suffixes, added to words, and free-standing function words (prepositions and articles). Different language-types make different uses of these, including cases added to each noun, tense and aspect markers added to each verb, and agreement markers linking nouns, adjectives, and determiners. Children have to identify each inflection, its meaning, and where it is used on each word class. They start to add modulations to their words as soon as they start to combine words (and may understand some of them before this). They use regular forms as their starting point and over-regularize irregular forms. They show some consistency in the order of acquisition for different modulations, depending on the semantic complexity of each grammatical morpheme. Semantic complexity, formal complexity, and frequency all play a role here. Children may initially rely on filler-syllables, and only later produce the relevant form. Word class plays a role here, since the choice of grammatical morphemes depends on this. Initial use of grammatical morphemes may be limited to specific words and only later extended. The same holds for agreement in gender and number.

This chapter details two types of drumbeats used by drummers when playing irregular-meter grooves based on large repeating spans (ten or more beats or pulses). The types – punctuated and split – differ with regard to the subdivision of the repeating cycle. In punctuated irregular grooves an established meter is interrupted at regular intervals by isolated measures in another meter. In split irregular grooves, the cycle is divided into two or more subsections of approximately balanced lengths. The drums play a critical role in decoding these subdivision patterns. Many irregular-meter drumbeats can be related directly to the familiar common-time backbeat, and the ways that an irregular-meter drumbeat diverges from that regular-meter archetype provide a ready guide for metric analysis. At deeper metric levels, drumming conventions such as fills serve as structural landmarks. The theory of punctuated and split metric structures demonstrates the centrality of drum-kit syntax to the performance, perception, and analysis of metrically irregular rock music.

Chapter 4 introduces basic differential equations and boundary conditions for gravity waves propagating along a water surface. Assuming low wave amplitudes, equations are linearised. Then a quantitative discussion is given for harmonical (sinusoidal) waves propagating either on deep water, or otherwise on water of constant depth. Phase and group velocities are introduced, and then formulas are derived for the potential energy and the kinetic energy associated with a water wave. A closely related result is an important formula for the wave-power level, which equals the wave’s group velocity multiplied by the wave’s stored – kinetic + potential – energy per unit of sea surface. An additional subject is the wave’s momentum density. A section concerns real sea waves. Further, circular waves are mathematically described. Two sections of the chapter concern mathematical tools to be applied in Chapters 5–8 of the book. A final section considers water waves analysed in the time domain.