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FL Studio (formerly Fruity Loops) is a DAW that focuses on being highly customizable. It is mostly known for its advanced piano roll and easy to use interface, and is used by many big EDM musicians. With a quick and efficient transition between its Pattern and Arrangement(Playlist) modes, the workflow can be boosted to great lengths.
SpecsUpdate
Pros
Pro Intuitive piano roll
Piano roll is a FL Studio's instrument step sequencer. It is considered to be among the most intuitive and flexible tools for quickly creating patterns and manipulating all aspects of each note. A single left click inserts a note, while a right click deletes it. It's possible to mute notes, splice them, stretch them, add shuffle, etc quickly.
The Piano Roll caters for those new to Music Theory as well, containing an array of chords from which to choose, be it a Major, Minor, Minor 5th, Minor 9th, what have you.