4MD Format is used in Halloween Harry for music. It is a modified version of the MOD music format using lower quality 4-bit signed sample data (2 data points per byte) instead of 8-bit signed sample data used by regular MOD files. The files can be converted to regular MOD files by upscaling the 4-bit sample data values to 8-bit values.
Some of the Halloween Harry 4MD files include non-existent pattern entries in the 128-byte pattern table past the specified count of patterns. This confuses some MOD players that detect the number of patterns by scanning for the highest entry number in the whole pattern table regardless of the specified count of patterns. Since the sample data starts after the pattern data, this causes all sample data to be offset resulting in distorted playback. Thus, the pattern table may need to cleaned of entries past the specified count of patterns to ensure compatibility in a wide assortment of MOD players.
The following tools are able to work with files in this format.
|Name||Platform||Play?||Create new?||Modify?||Convert/export to other?||Import from other?||Access hidden data?||Edit metadata?||Notes|
|4MD2MOD||DOS||No||No||No||Yes; .mod||No||No||No||Does the conversion incorrectly by halving the length of each sample instead of upscaling the sample data values|