During the in-flight portion of a flight review, the Private pilot, who did not have a current flight review at the time of the accident, forgot to extend the landing gear during a practice soft-field landing. The flight instructor giving the flight review was aware the pilot had not put the landing gear down and, while the aircraft was on final approach, told the pilot multiple times to execute a go-around. The pilot, who said he did not hear the command to go around, landed the aircraft with the gear up. The flight instructor thought the pilot had heard him, and was going to do a go-around, and therefore did not take remedial action. The pilot did not use a checklist.
