Minor Nitpick!! You got the spelling wrong for promotions at https://next.duckduckgo.com/about?t=i&kd=-1

Thanks.. fastmail.fm is pretty good

you might need to look into http://aws.amazon.com/elastictranscoder/ if it can satisfy your use-case

Take a look at the Zencoder (YC W10) API: http://zencoder.com/en/

It's since been acquired by Brightcove. [Disclaimer: I work there.]

The audio file must exist somewhere, it offers no live audio support. So the bottleneck would be at the beginning rather than the end.

Elastic Transcoder doesn't support this natively, we ran into this issue so ended up rolling our own solution as the commercial versions were incredibly expensive for a non-profit.

wow!