Percussion instrument and Steel drum

Percussion instrument noun - A musical instrument in which the sound is produced by one object striking another.

Steel drum and percussion instrument are semantically related. In some cases you can replace phrase "Steel drum" with "Percussion instrument", this phrases are similar.

Steel drum noun - A concave percussion instrument made from the metal top of an oil drum; has an array of flattened areas that produce different tones when struck (of Caribbean origin).

Percussion instrument and steel drum are semantically related. You can use "Percussion instrument" instead a noun phrase "Steel drum".