The Hydrogen user interface is designed so that it can be used entirely with the mouse, with the exception of text entry.

Most actions are performed with the left mouse button (or mouse wheel) and implement what should be the most obvious behaviour for any control. The right mouse button may sometimes perform an alternate action or brings up a context menu. Some common controls also have alternate actions accessed by clicking while holding a modifier key:

All rotaries and faders can also be set by using the keyboard. First, you have to click the widget for it to be focussed, indicated by a coloured highlight (orange per default). Now, you can enter numerical input via your keyboard. All numbers and dots are concatenated. If you want to reset your input or start a different one you can either press ESC or wait a couple of seconds.

3.1. Keyboard usage in Editors

The keyboard can also be used for navigating and editing in the Pattern and Song Editors, using a combination of

• ↑|↓|←|→ : move the keyboard input cursor's position, or adjust values under the cursor.

• Shift + ↑|↓|←|→ : can be used to make selections of notes or pattern groups as if the mouse had been dragged over them.

• Enter and Return : generally performs the same action as a mouse click, but can also start or end a move (or copy) of items in the same way a mouse drag would.

• Tab and Shift + Tab : move between the Pattern, Song and Note Property Editor.

• Delete : delete notes or patterns.

• Esc : cancels an ongoing selection, move or copy.

	Note
	The keyboard input cursor is hidden from view until one of the above keys is pressed. This keeps the display clear and uncluttered when using the mouse. You can alter this default behavior in the General tab of the Preferences.

Most other keys on the keyboard can be used to play samples (see Virtual Keyboard).