Michael Morpurgo, author. A child needs to feel from the very start that she or he is wanted and loved. They should grow up in the soil of affection of care. There is no replacement for that, it is the most important thing.
American bugler in the Navy, 1917. The bugle is a very simple brass instrument. It has no valves or other mechanisms, the only way the player has to control the pitch is changing the shape of his lips. This means that only notes from the harmonic series can be played.
Sometimes the venerable pre-transistor vacuum tube is referred to as a valve as well. The simplest valves are one way-flap mechanisms that allow flow in one direction and shut with back-flow pressure to stop flow in the direction of origin.