If the checkbox is clicked, define in millisecond the time duration of each note. Else, the note stop when you stop to click on a note.
You can define the maximum value of the range with the input 'Max ms'.
You can play piano with the keyboard of your computer. Click on the 'Keyboard mapping' button to show the configuration.
Use your keyboard button 'MAJ' and 'CTRL' to up and down octave. You can also click on the octave number to do this.
Under the piano, use the octave number area to slide left and right.