Irama is the rhythmic relationship between the balungan and the elaborating instruments. It is often expressed as a ratio, and each irama is also known by an Indonesian term. The ratio expresses the number of bonang/gender notes are played for every beat in the balungan. Please note that the panerus versions of the bonang and gender will play twice as many notes in the same time period as their barung counterparts, but this is understood as being part of the same irama, not as one instrument being in one irama and another being in a different irama. The whole gamelan is in a particular irama, not just one player.
       5       3
       5       3
Very fast
Lancar1:1 in anticipation
   5   .   3   .
       5   5   3   3
   5 5 3 3 5 5 3 3
Very Slow

On Javanese Rhythm

Javanese rhythmic structures are based on duple (2) and quadruple (4) divisions of units of time. This is a very common occurance in Western music as well, but with some important differences.

In Western music, a group of beats, as one would find in the meter 4/4, the first beat receives the strongest accent, the third beat a lesser accent, and the second and fourth beats are "weak", or unaccented. In Javanese music, the exact opposite is true. The last beat of a group of four is the most important, the second is somewhat less so, and the first and third the least so. This is true at every structural level.

For example: the Gong is normally divided into 2 or 4 kenongs. The last of these kenongs is of the greatest importance, as it coincides with the gong.

		      N   N   N   (N)

The kenong is then divided into 2, 4, 8, or 16 beats by the balungan (even more in large gendhing), which will be in groups of 4, called gatras. In each gatra, the last note will be the one that is accented. Here are some examples of balungan/kenong relationships (X=balungan note):

		      N   N     N    N
2 beats/kenong      X X X X   X X X (X)

			  N         N         N          N
4 beats/kenong      X X X X   X X X X   X X X X   X X X (X)

				    N                   N
8 beats/kenong      X X X X   X X X X   X X X X   X X X X

				    N                    N
		    X X X X   X X X X   X X X X   X X X (X)

The last note in each gatra is called a seleh, and is the most important note. Many elaborating instruments play patterns based on the seleh only, with little or no regard to the other notes in the gatra. And when the elaborating instruments divide the beats into 4 part, or 16 notes to gatra, again the 4th, 8th, 12th, and 16th notes of their patterns will be the ones that coincide with the balungan beat.

	     5    3    5    6       3    5    6    i
Gender: | 535. 535i 565i 56i6    565. 5653 656. 656i
	| ...2 1653 .535 6126    ..61 212. ..32 1261

This process is true for duple divisions of the beat as well. In a piece where the bonang divides the balungan beat into 2 (irama tanggung), it will do so by taking each pair of balungan notes and playing them twice, at twice the speed, such that the 4th bonang note coincides with the 2nd balungan note:

Balungan:       2   3   2   1     3   5   3   2
Bonang:       2 3 2 3 2 1 2 1   3 5 3 5 3 2 3 2

Notice again how on the "weak" beats, the first and third, the pitches of the instruments do not match, but rather only on the "strong" beats, the second and fourth.This is especially apparent in the lancaran form. The lancaran divides the kenong into 4 balungan beats, but the "weak" first and third are silent. The bonang fills in the holes left by the slenthem, playing in octaves on the pitch of the kenongs. However, the kenong takes its pitch, not from the last note of the gatra, but from the last notes of the second and fourth gatras:

		  N5        N5        N6         N6
Balungan:   . 6 . i   . 6 . 5   . 6 . 5   . i . (6)
Bonang:   | 5   5     5   5     6   6     6   6
	  | 5   5     5   5     6   6     6   6