Our service, 80legs, will let you easily do this. We let you specify seed links, how deep you want to crawl, and control many other aspects of the crawl. By default, we control the hard bits, like redirects and spider traps, but if you want to override our default functionality you can easily insert your own code to do it.
Our default functionality will let you identify mp3 files by regex or keyword, but if you need something more sophisticated you can override that too. I'm pretty sure, based on what you've said, that you could simply put in a few parameters and start running some jobs within a few minutes of getting started with 80legs that will do exactly what you want. If not, adding custom code to 80legs is pretty simple too.
Just send us your contact info on our website (http://www.80legs.com) and mention HN and I'll make sure you get a beta invite. BTW - we're still in private beta and the service is still free for right now.
Our default functionality will let you identify mp3 files by regex or keyword, but if you need something more sophisticated you can override that too. I'm pretty sure, based on what you've said, that you could simply put in a few parameters and start running some jobs within a few minutes of getting started with 80legs that will do exactly what you want. If not, adding custom code to 80legs is pretty simple too.
Just send us your contact info on our website (http://www.80legs.com) and mention HN and I'll make sure you get a beta invite. BTW - we're still in private beta and the service is still free for right now.