Yes. MIDI packs or MIDI files are used by producers to save melodies, drum, and percussion patterns. If a producer does not have the equipment to create their own complete music productions (e.g. keyboard, synthesizers), they may use downloaded VST plugins with built-in synths or keyboards which can be connected through any DAW software package that allows for them such as Logic, Pro Tool's etcetera.
MIDI packs are also an important instrument to learn if you want to understand how a song is made from start to finish because it applies all of the sounds of a track together.