Look for "The Complete DX7" by Howard Massey. Very rare to find a printed copy, but a PDF scan of it is probably still up on Archive.org. By far the best manua

Look for "The Complete DX7" by Howard Massey. Very rare to find a printed copy, but a PDF scan of it is probably still up on Archive.org. By far the best manual and sound design "how-to" for the DX7, or for FM synthesis in general.