Yes, You are right about the meaning an agents liaise with composers and performers. An agents is needed through the mediation of composers and institution like a theaters and other,- for to set a creations and this agent could absolutely help representing a creations and would find all opportunities to set a music, to collaborate with musicians, institutions and of course to be in a solving of all this problems.
Talking about an agent experience or knowledge is important only: this agent could be absolutely able to find a possibilities to set, represent and promote a music to musicians, theaters and so on.
Pay, -of course from a royalty of composer's concerts, performances,- there's an agreement between agent and composer.
Hmm I hate to break it to you guys, but an agent in music does nothing except negotiate contracts. You might get a job or 2 as a relation to having that agent, but the agent does not bring you work. The agent, of which there are only around 300 or so certified and real agents, only steps in as your negotiator when you have a job landed. So - you get a job (or your manager) and the agent comes in and gets all the terms you want and (hopefully) better money and points than you would have on your own. Then it goes to the lawyers who make sure that all the points that the agent put together are legal and do not conflict somehow
people who bring business in for you would be a manager, talent scout, A&R exec, publisher. Agents just assist in negotiating once you have work already. "Agent" is a very specific profession and there are only a handful of actual accredited "agents", probably totaling several hundred worldwide at the most, and most of them being in LA. Taxi.com is an A&R service, one that introduces artists to labels and studios. I am not familiar with StarNow.co.uk. In the world of media composing ultimately there is nobody (*nobody*) that will bring you work, its all up to you to use your own business savvy. Even top composers in Hollywood are responsible for their own relationships, and usually stick together - look at how many films John Williams has scored that werent Steven Spielberg or George Lucas
There are a lot of great points being made here, but one clarification should be made in regards to whether or not agents and managers will get you work.
It differs from state to state and I have zero experience in what happens outside of the USA, but in California, managers are not legally permitted to procure work for clients - only advise them. Agents, on the other hand, *are*.
Therefore, it is pretty unheard of that an agent in Hollywood is not actively seeking projects for their top-tier clients. Now, that being said, any agent at the "Big 3" will typically have A, B, and C-level clients, and the majority of the work gets handed to A-listers, sometimes B. C-list clients are out hustling for jobs, typically in TV or in independent film, and cannot count on their agents to find them their next gig.
If you have an Agent who is working for you & they know what they are doing, it can work well. For The fairly well published Composer it is still difficult to get your foot in the door. A good Agent who has faith in your music & ability & will work for you can match you up with a good film. Music Supervisors are always being flooded with Composers looking to score a film. A GOOD AGENT is hard to find, yes. But, at times they are a necessary evil just like Attorneys