Queue identification

At least one non-transitory computer-readable medium comprising program instructions that are executable by at least one processor such that a playback device is configured to:

• play back first media items from a playback queue;
• receive, via a network interface from a first controller, a first command, the first command instructing the playback device to add second media items from a first source to the playback queue;
• before adding the second media items to the playback queue, determine that contents of playback queue are compatible with the second media items, wherein the contents consist of the first media items;
• carry out the first command based on the determination that the contents of playback queue are incompatible with the second media items, wherein the program instructions that are executable by the at least one processor such that the playback device is configured to carry out the first command comprise program instructions that are executable by the at least one processor such that the playback device is configured to add the second media items to the playback queue;
• receive, via the network interface from a second controller, a second command, the second command instructing the playback device to add third media items from a second source to the playback queue;
• before adding the third media items to the playback queue, determine that the contents of playback queue are incompatible with the third media items, wherein the contents consist of the first media items and the second media items;
• and
• carry out the second command based on the determination that the contents of the playback queue are incompatible with the third media items, wherein the program instructions that are executable by the at least one processor such that the playback device is configured to carry out the second command comprise program instructions that are executable by the at least one processor such that the playback device is configured to replace the contents of the playback queue with the third media items.

A method to be performed by a playback device, the method comprising:

• playing back first media items from a playback queue;
• receiving, via a network interface from a first controller, a first command, the first command instructing the playback device to add second media items from a first source to the playback queue;
• before adding the second media items to the playback queue, determining that contents of playback queue are compatible with the second media items, wherein the contents consist of the first media items;
• carrying out the first command based on determining that the contents of playback queue are incompatible with the second media items, wherein carrying out the first command comprises adding the second media items to the playback queue;
• receiving, via the network interface from a second controller, a second command, the second command instructing the playback device to add third media items from a second source to the playback queue;
• before adding the third media items to the playback queue, determining that the contents of playback queue are incompatible with the third media items, wherein the contents consist of the first media items and the second media items;
• and
• carrying out the second command based on determining that the contents of the playback queue are incompatible with the third media items, wherein carrying out the second command comprises replacing the contents of the playback queue with the third media items.