Xenharmlib, a music theory library, has released version 0.4.0, marking a significant advancement with the integration of Just Intonation and other complex tuning systems. The library's core has been refactored to accommodate not only equal-division temperaments but also tunings with multiple generator intervals, enabling the representation of a vast spectrum of musical traditions, from Byzantine and Renaissance music to Indian classical and Arabic Maqam.

This update introduces support for Just Intonation via the Prime Limit Tuning construct, allowing for the creation of scales based on pure intervals (fractions like 3/2). Xenharmlib now implements transposition mathematically soundly, unlike traditional scalar transposition that can lead to inconsistencies. The library also enables the design of custom regular temperaments using Multi-Generator Tunings and introduces full interval arithmetic, a crucial feature for theoretical applications.

Version 0.4.0 further enhances analytical capabilities with new harmonic primitives: Sequences for conceptualizing note successions and Interval Fans for describing relative distances to a tonal center. Additionally, it supports the calculation of interval class vectors, essential for scale analysis, particularly in post-tonal music. The documentation has also been comprehensively revamped for easier navigation and understanding of these new features.