When entering the UK, the first thing to clarify is, depending on the reason for your trip, which is the correct "entry route" or with which status you are entering the UK. It already plays a role here whether you belong to the group of "visa-nationals", i.e. whether your nationality requires you to apply for a visa, or whether you can enter as a "non-visa national". For most countries, "non-visa national" applies. A list of visa-nationals can be found here.
When you arrive in the UK, there are different ways to register your entry: either automated and electronically via the ePassport gates (passport with ePassport function is required!) or directly with an officer. The automated ePassport control is intended for all entries that are not subject to a specific regulation, such as tourist entries. In principle, EU citizens still do not need a visa for visits and business trips of up to six months, which would have to be applied for separately in advance. Therefore, the ePassport control would be the usual entry route for this purpose. However, as soon as you want to enter under certain conditions or for certain financially motivated business reasons, you have to report the entry to a border official. In the case of artists, certain conditions include, above all, paid performances or other fees for services. When selling goods, such as merchandise or works of art, it is also necessary to check which "entry route" or status is to be chosen and which further customs formalities are to be observed.
Note: A passport is always required for entry into the UK. Identity cards are not accepted for entry!
In this German-language video, you'll find a general introduction on mobility issues for touring musicians and bands based in Germany who intend to travel to the UK.