Note blocks can be crafted by placing eight wooden planks in a square around the edges of the crafting grid and one redstone dust in the center. The type of wooden planks used to craft a note block is irrelevant. Any combination of planks will work. This block can be used to generate musical tones or for aesthetic purposes. In conjunction with redstone circuitry, note blocks can be used to create systems that act as a doorbell, an alarm system, or to play a song when activated.
A note block will play a note when hit or when powered by redstone. Redstone current only causes the note to play once, even if it is a continuous current. A note block must have at least one block of air above it to play a sound. Notes can be heard up to 48 blocks away. Each time a note block plays a note, a note particle will fly out of the top, with the color depending on the pitch (but not the instrument).
In order to wire Note Blocks to play a note, power must be applied to the side of the Note Block using Redstone Dust and a Switch or Redstone Torch, or to the bottom using a redstone torch directly. Simply placing a switch or pressure plate on an adjacent block or providing power to the block beneath the Note Block will not work.
If one wants to get a richer tone in the song/sound they're creating they can bind different notes together into a chord, just like in most instruments. This will not only get a better sound to the song, it will also be simpler to place the Redstone.