You searched for: “harmonization
harmonization, harmonisation
1. A piece of harmonized music.
2. Singing in harmony.
3. In international law, the process whereby different countries adopt the same laws.
4. The changing of government regulations and practices, as a result of an international agreement, to make those of different countries the same or more compatible.

For example, with tariffs, this means making tariff rates more similar across industries and/or across countries.