mixing/mastering for long player records

Emdprodukt

Member of Dude Castle 69
Jun 26, 2007
2,520
1
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Kiel, Germany
A band I know is going to release a split LP with the black metal band "Endstille" (I hate blackmetal but they seem to be pretty famous) which seems to be a good oportunity for me.

So they asked me to mix and master two of their songs for myspace and the LP. What's important when mixing/mastering for a long player record?