About Drum Heads
As long as there have been drums they have been topped by drum heads. Originally these were made of animal skins but since the 1950s those have been largely replaced by synthetic materials that last longer and have better resistance to the effects of temperature and humidity. With the advent of these new materials came new fabrication methods and today's drum heads may have one or two layers. In the latter case there are variants - the Evans Hydraulic Bass Drum Head for instance - which have a thin film of oil sandwiched between the layers to suppress overtones. Other heads such as the Remo FiberSkyn series are designed to replicate the sound of vintage skin drum heads as closely as possible.
Each drum requires a properly-sized head designed for its construction and playing style so as a general rule they are not interchangeable. A snare drum head is not the same diameter as a tom-tom drum head for example - and the tom head is not designed to be in contact with a metal snare. Drum heads may be purchased individually or in drum head pre-packs that can outfit an entire drum kit. These can be economical choices for many drummers since the heads should be replaced regularly: typically at 12-month intervals or sooner if the installed drum heads are beginning to show too much wear or if the sound quality has deteriorated.