Probly b'cause two things: number one, it seems t' have been a part o' th' Fat Lute site which sort o' folded an then re-opened, much diminished, so that page mebbe ain't there any more, or got re-named or something, an B) it' would've been terribly out o' date anyways. Back in them years, we was creatin abc files with something called th' LOTRO MIDI Player (or somethin like that), or a website called Firefern's Midi Transcriber (or somethin like that). But both o' them softwares was superseded fer ease o' use mebbe 5 years ago by this thing called Maestro (can be downloaded here: https://github.com/digero/maestro/releases).
Basically, y' open a song in Maestro, an it shows all th' tracks o' th' MIDI, an lets y' assign LOTRO instruments to 'em, an then lissen t' what it sounds like, without havin t' actually get into th' game an load up all th' parts. Then it will convert yer substitutions into .abc format, so LOTRO's Music System can read 'em.