OpenMPT - OpenMPT is a popular tracker software for Windows.
MuseScore.org - Create, play back and print beautiful sheet music with free and easy to use music notation software MuseScore. For Windows, Mac and Linux.
SunVox - SunVox is a small, fast and powerful modular synthesizer with pattern based sequencer (tracker).
Guitar Pro 7 - Create, play and share your tabs
PxTone Collage - A music editing software, capable of using common sounds, custom sounds, and everything in between to make surprisingly good music. Originally in Japanese, but easily fixed.
Finale - Finale, the world standard for music notation software, lets you compose, arrange, notate, and print engraver-quality sheet music.