1: Steal an old Robert Johnson blues track. Preferably one about being lonely, or flood defence mechanisms.
2. If the lyrics make too much sense, change them. Nip down the library and get out a copy of Tolkein’s Simarillion (the one where the first twenty pages are thumbed and the rest are as clean as the day the book was bought). Lyrics can be taken verbatim. Alternatively imagine yourself to be a Viking.
3. Beef up the percussion by getting a man who is physically designed only to hit things very hard, and who only wants to hit things very hard, to hit something very hard. Repeat.
4. Add twiddly guitar bits to the song, in case the track had any original emotional merit. Layer a twelve string guitar in the background as well, just to be on the safe side.
5. Try to persuade your bass player to puff a bit of flute over it. If he does, it is a ballad. Repeat step three slower. If he’s off flute this week, it is mid-tempo. If it ever gets fast, you are doing something wrong.
6. Find a castrato with 80 cubic metres of frizzy hair. Tell him to sing with feeling. Tell him also to howl, wail and generally make a tit of himself. If he ever gets round to singing any of the lyrics, its a bonus.
7. Repeat eight times. You now have an album. Name it something clever like – er – after the number of albums you have released. If this gets too high for you to count (say above four) use its name to describe the contents. Such as The Song Remains The Bleeding Same.

Voila. You are now Led Zeppelin. May you rot in prog rock hell.