An excuse for a very bad joke

It's a 1950s jungle movie, probably as politically-incorrect as only a 1950s jungle movie can be.

As our heroic explorers head through the virgin jungle, the sound of tribal drumming can be heard in the distance.

"When the drumming stops, we are doomed", says one of the native guides.

"What do you mean", asks the heroic explorer.

"When the drumming stops, we are doomed", relies the guide.

Then the drumming stops.

"We are doomed", cries the native guide in panic.

"Why", cries the explorer.

The guide stares at him and replies, "Bass Solo".