Howard Abrams has a nice post on working with key sequences. He shows how to set up personal key maps with a common prefix. Abrams likes to use 【F9】 as a prefix to several maps. For example, 【F9 m】 is for his music listening. A third character chooses a channel to listen to or, with 【s】, stop the playback.
Next, he considers how to set these key maps from a list of keys and music channels. Nothing too surprising in any of this but then he asks if he can have a single routine to set the keys for all his personal maps based on an input list. To do that you need a macro and Abrams provides one that takes a list containing information about all his personal maps and initializes them.
Finally, Abrams mentions hydra and notes that it’s what you need if you want to be able to repeat a key. For example, you might want a control that adjusts the volume up or down with 【u】 or 【d】. In a case like that, it’s convenient to be able to repeat one of the keys until the volume is at the desired level.