The visualization of sound presented in book form and accompanied by a CD-ROM by Carsten Nicolai, the creator of our successful Grid Index and Moiré Index titles. Ryoji Ikeda and Carsten Nicolai both work at the cutting-edge of contemporary electronic music and sound art. In 1999, the two artists initiated the joint project cyclo., which is devoted to the visualization of sound. In their shared work, they generate new hybrid forms of audiovisual art and expand the possibilities of digital technology. The project's first publication is cylco. id, a book and included CD-ROM that offer a multimedia and interactive documentation of the audiovisual material that Nicolai and Ikeda have collected, researched, and created since they began working together. The featured images are formed by the metering of sound bits that have been selected by the artists with meticulous care according to their acoustic and illustrative potential. The material collected in cyclo. id is pure elegance, and its rich structural complexity is inspiring for anyone working with sounds and forms. Visually fascinating, the examples also invite the viewer to play and experiment with them. The open-source format of the digital files makes it easy for creatives to further develop the data and use them in their own work. Carsten Nicolai, the renowned German contemporary artist who successfully documented fundamental visual structures in Grid Index and Moiré Index, has been working at the intersection of art and science since the early 1990s. The work of Ryoji Ikeda, one of Japan's leading electronic composers, explores the physical properties of sound.