It is always good to have a place to go to to find out information, and while the LOTRO Wiki is good, it doesn't always include value judgements, or insights into the game.
This is a Work In Progress, a collection of those links that the officers and the kinfolk of Immortal Souls feel are of benefit to others in the kin. If you have suggestions for other sources, let us know so we can review and add them.
Note: Not all ABC files are crafted with care. many are straight MIDI rips, or single finger keyboard. Without musical arrangement, or careful tuning, some are plain awful. Download an ABC file player, and listen to the music file before you play it in-game, better still, get a second opinion from someone who is not in game. Better to judge and weed out the terrible before subjecting other players to a cacophonic nightmare.