A time signature is two numbers presented and expressed as a ratio such as 3/4. The numerator may be any integer and the denominator any power of 2, i.e. 1, 2, 4, 8, 16 ... which division levels are the binary subdivisions of the whole (note). Thus the time signature ratio is the length of the measure which it defines. Examples are shown in figure 1 below. Each beige rectangle represents the length of one eighth note.

Meter

The traditional conceptual artifice for dealing with the small scale temporal divisions of music is the meter.  A meter defines a regular quantized framework which is assumed to provide the most fundamental level of temporal expectations  A meter fills or defines the length of a measure and specifies a pattern of accents and their implied beat groupings and which pattern is repeated in every occurrence of a measure in a given meter. A meter is the combination of a time signature and a specified method of accent grouping.

Of course, in the end -- in the hearing of the music -- meter is not an artifice, it is a matter of direct aural perception. It is the events – their timing, emphasis and length that determines when we expect to tap our toes. One can segue between meters compositionally but the Meter class, like standard notation, can only specify by a "time change" some point in time when one meter is thought or computed to be dominant over others that might be implicated by actual events. Recently Bayesian techniques that compute perceived meter have been developed and will likely be of use to Zylaphon in this regard.

For the most often used time signatures the accent groupings are specified by conventions drawn from common practice which recognizes several types of meter.  Zylaphon recognizes five distinct kinds of meter including user defined accent patterns.