He has a variety of choices when it comes to the pipes. Although some are made from copper, the majority are forged out of a combination of tin and lead. Lead has a little mellower tone to it. So we like to use that for the flute sounds. We use zinc for bass pipes - lead is just too heavy.
Wooden pipes are usually smaller and produce mellow woodwind sounds.
It depends on what you want. The leathers are used in various inner workings of the organ. As the organ is being built, the congregation also needs to check to see if changes are needed in the sanctuary's acoustics and if any part of the sanctuary needs to be reinforced to carry the heavy load. Acoustical tile is very bad for a church. A hard surface that reflects the sound is best.