There are various approaches to notating rhythm in alternative music notation systems. This page gives a brief overview of some of these approaches, and provides a place to collect additional information about them.
Traditional and Modified Traditional Rhythm Notation
Many alternative music notation systems use the established rhythmic symbols of traditional notation. Sometimes these are adopted with slight modifications, often introducing new ways to differentiate between quarter notes and half notes so that hollow and solid notes can be used to help indicate pitch (see this tutorial: Noteheads and Pitch ). This provides continuity with traditional notation, but does not really attempt to improve upon the traditional notation of rhythm.
Proportional Rhythm Notation
Some alternative music notation systems use proportional spacing on the time-axis of the staff (whether vertical or horizontal) to indicate rhythm. Klavar Music Notation is a well-established example of this approach. To help the reader see the intended rhythm, Klavar uses not only the usual solid bar lines but also dashed beat lines.
(Proportional spacing has also been used by many composers, starting in the 20th century, on a traditional staff with traditional pitch notation. Typically this is done when the composer doesn’t wish to imply a meter or a regular beat, and often the composer uses black noteheads without stems. This approach is referred to as “proportional notation,” “time notation,” or “spatial notation.” The first of these terms is also used by music historians to refer to mensural notation, however.)
Alternative Symbol-Based Rhythm Notation
Other alternative music notation systems introduce more thoroughly re-designed rhythmic symbol systems. An example of this approach is Mark Gould’s rhythm notation system for Equiton, as described in these presentation slides (Gould_Equiton_Slides.pdf) that were originally posted on his website. Another example is Panot.