Some cells are shaded. Shaded cells cannot have clues in them or instruments. Every unshaded cell is part of exactly one instrument.
Four instruments are drawn with lines: the gambang, saron, siter and suling. Draw one to three edge-to-edge lines in every cell of these. Within any one cell, the lines will be entirely either vertical or horizontal. Also draw the borders between two instruments of lines; a border anywhere else doesn't matter.
Gambang: typical Gamelan rectangle, clued typically: three or more identical cells, numbered with its gamelan sum, the region's size in cells times the number of lines inside any cell in the region.
Saron: color inverted gambang that subtracts from its margin clues. Its own number is positive, so a margin number may be negative.
Siter: a normal gamelan rectangle, but with one end replaced with a diagonal line that goes between cell intersections, cutting any strings (lines) past that diagonal off. For example, a 2x4 can only be cut into a siter in one way: having the top/bottom cut off by a 2-cell diagonal, rendering the total area 5 + .5 + .5 = 6. A siter has two strings in every cell, and they always run toward the diagonal. Its number is its area x lines (12 for that example). A cut cell counts 1 in its margin.
Suling: a 1xN or Nx1 where N>3; each cell must have 2 lines (though spread out so an unshaded pearl fits perfectly between them), and the lines must all run towards each other (lengthwise, so a vertical suling always has vertical lines). The suling will have some number of cells that bear unshaded pearls, at least one. Its number is its size in cells * number of pearls. Its lines count in the line margins, and its pearls in the pearl margins.
Bonang/reyong/kenong are all kettle gongs. A bonang must be a 2xN or Nx2 of unshaded pearls where N>2. A reyong must be a 1xN or Nx1 of unshaded pearls where N>2. A kenong must be the incomplete, orthogonally contiguous outline of an MxN rectangle where M, N >2, lying entirely on the board. It must have an area of at least 5; must not sit entirely in a row or column; and must be missing at least 2 cells. Two kettle gongs may not touch royagonally. When cluing kettle gongs, numbers refer to the total area of the kettle gong (the total number of cells they occupy).
Gong: must be a huge unshaded pearl occupying a 2x2. Never clued. It may touch a kettle gong, and it counts once in each of its two rows and two columns.
A number sits inside its instrument, and there will be at most one number per instrument. A number doesn't say which instrument it's in. Some pearls can be clued by being shown on the board.
Left/top margin clues are gamelan sum lines; bottom/right are number of unshaded pearls. A line margin counts the total number of lines in the counted cells that face toward that number.