Rhythm as Compression Under Constraint: Independent Derivation of Sub-Limit Dynamics from the Domain of Temporal Iterability

We derive the four structural properties of sub-limit dynamics from the rhythmic domain. The rhythmic pixel is the ordered pair of consecutive temporal intervals (Δt₁, Δt₂): the first configuration in which iterability becomes classifiable under a finite temporal resolution threshold L (JND ≈ 2–3%). This is the third second-order pixel in the framework, after melody (M2) and evolution (B4). The consumption type is T3, the regime R2. Rhythm is classified as Q-family G (compression, Q28): the infinite continuum of temporal ratios collapses into a finite vocabulary of metric classes under L. This completes the three-family structure of the musical domain: F (harmony, M1), E (melody, M2), G (rhythm, M3), structurally isomorphic to the three-family structure of DNA. The central contribution: rhythm provides the first empirical instantiation of the framework's temporal operator ω as a physical observable. Rhythm is not modelled by ω, it is ω made audible. Twentieth verified domain.