His explanation for this is given in the sleeve notes, where he says that some of the tracks ('Mars', 'Two Friends', 'Two Brides', ' Slave', 'Frog' and 'Get Me Out of This') were recorded in a more unrehearsed and experimental way than the others.
His account for this is outlined in the sleeve notes, where he mentions that some of the tracks ('Mars', 'Two Friends', 'Two Brides', ' Slave', 'Frog' and 'Get Me Out of This') were recorded with a more relaxed and experimental approach than the others.