ProTracker
ProTracker is a music tracker for the Amiga platform. A free software tool that required no additional equipment, it became popular in the early 1990s with both amateurs and professionals, allowing for sample-based music in the MOD file format. Introduction. "ProTracker" allows the user to create sequences of notes called "patterns", which are chained together to form a complete song. Music created in ProTracker uses the MOD file format. It was initially developed for the Amiga line of computers, but was later made available for other platforms such as the Atari ST. Features. Building upon the features of  previous trackers such as Ultimate Soundtracker and NoiseTracker (of which ProTracker's code is based on), ProTracker came equipped with a built-in sample editor and a keyboard split function to assign multiple instruments to different regions of the keyboard. Later versions also extended the MOD format by increasing the maximum number of patterns from 64 to 99, and adding a number of additional effects. "ProTracker" is capable of playing back music at the correct speed on both NTSC and PAL computers. Previous tracker software used playback routines which were synchronized to the refresh rate of the screen, which would  cause music composed on one standard to sound incorrect on computers of the other standard due to the differing refresh rates. Open source remake. There is an ongoing effort since 2010 to make an open source software clone of ProTracker for modern platforms at GitHub. The also "ProTracker 2.3D clone" named software is developed under the BSD 3-Clause License and available for Windows, Linux, and macOS.