Loom is a graphics adventure game originally released in 1990 by Lucasfilm. It was developed by Lucasfilm and was the fourth game to use the SCUMM adventure game engine.
Different with other LucasArts games, Loom is based on a serious and complex fantasy story. With its experimental interface, it eschewed the traditional paradigm of graphical adventures, where puzzles usually involve interactions between the game character, the environment, and multiple items the character can take into their possession.
Loom's gameplay centers instead around magical four-note tunes, or draft, that the main character, Bobbin Threadbare, can play on his distaff. Each draft is a spell that has an effect of a certain type, such as "Opening" or "Night Vision". Drafts can be learned by observing an object that possess the qualities of the relevant draft; for example, examining a blade while it is being sharpened gives the player the "Sharpening" draft.
Some drafts can be reversed by playing their notes backwards, so the "Dye" draft played backwards becomes "Bleach", while others, such as "Terror", are palindromes and can not be reversed in this manner. The player's abilities increase over the course of the game, with more and more powerful drafts. At first, only the notes C, D and E are playable, but by the end of the game F, G, A, B and C' (high C) are also available.
Loom was also the first game to follow the LucasArts Game Design Philosophy, which states that the player will never be killed or forced to restart the game and won't have to "spend hours typing in synonyms until stumble on the computer's word for a certain object".
You can download Loom, its manual and walkthrough here.