Train whistle sound effect

Several pitches blown at once, so what reaches the audience is a chord rather than a note. The front swells instead of snapping, and the tail runs on well past the blast.

Two quick calls, open and shut. Short enough to sit inside a cut where a held wail would run past the shot, and still unmistakably steam rather than compressed air.

A note shaped by hand at the valve, so the pitch swells and wavers the whole way through. It is the sound of a person operating a machine, which is something no horn can do.

A small single note whistle of the kind a yard switcher carries, thin and shrill with no chord in it at all. Reach for it when the locomotive is small and the scene is close.

Distance takes the top off the chord and leaves a faint return behind it. Level alone will not do that, which is why a wail simply turned down still sounds close by.

The moment before the note settles, when wet steam spits through the bell and the pitches have not found each other yet. It is the detail that separates steam from anything modern.