Diagramming messages on a service bus

I’m looking for a way to clearly diagram how multiple applications communicate via a service bus. The best I’ve come up with so far is a sequence diagram, but I really don’t like that. Sequence diagrams imply some sort of sequence and that’s really not what I want. Since every service communicates with the service bus and sequence diagrams place each service on a separate column, as the number of services increases, you end up with a lot of overlapping arrows.

For example, given 4 services FOO, BAR, BAZ, and QUX:

• Foo publishes messages of type publish and regen.
• BAR publishes messages of type requeue.
• BAZ subscribes to messages of type publish, regen, and requeue, and publishes messages of type transmit.
• QUX subscribes messages of type transmit.
• Any service can publish any message type at any time (there is no implied sequence).

What kind of diagram should I use to clearly and unambiguously represent this information?

Here’s the best I’ve come up with so far:
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