Changing LC filter passband width
Adding resistance to the LC "tank" circuit will widen the bandwidth, but will ruin the Q of the filter at the same time.  This is a basic tradeoff.   The "Q" (or quality factor) is a measure of how much on-frequency signal gets through, versus how much it can reject the off-frequency signals.

Real schemes to produce wider bandwidth filters use multiple LC's in various combinations, producing a "filter network".  It's still difficult to vary the bandwidth without switching components in or out.

Modern digital signal processing techniques can accomplish these things, as they are substituting "adding more circuits" with "adding more logic elements" and program code.