Ableton's tutorial channel walks through the Rhythm Generator in Live 12, showing how to build a drum pattern inside a drum rack one parameter at a time. The Generate button is on by default, meaning any parameter change updates the clip in real time, though you can switch to a manual apply workflow if you prefer more control over when changes are committed.
Steps sets the total number of steps in the pattern, and Density controls how many of those steps contain notes. The Pattern parameter cycles through different rhythmic arrangements, and more steps unlock more pattern variations. Step Duration sets the length of each step, and Shift moves the entire pattern earlier or later in time.
On the velocity side, you can set a base velocity for all generated notes and a separate velocity for accented notes. The Freq control determines how often accents appear, and the arrow buttons shift the accent pattern left or right independently of the note pattern.
The Split slider adds a final layer of variation, setting the probability that any given step will be subdivided into two equal notes instead of one. Together, these parameters give you precise, repeatable control over groove, density, and feel without drawing notes by hand.