Sound and music
Sound in Dragon Age is packaged using a program called FMOD. FMOD sound banks include the audio waveform itself, and can also include settings determining how the sound is played.
Voice over doesn't actually require you to work with FMOD, as the tools to package VO into FMOD sound banks are built into the toolset.
Placeholder voice over can be generated automatically by the toolset (using the default Microsoft text-to-speech engine that comes with your OS). This is intended as a way to easily produce a "rough cut" of a cinematic, giving an approximate feel for how long the line will last and allowing FaceFX to be generated.
Recording real voice-over for conversations is straightforward, though you'll need to keep track of the string IDs of the lines you're recording in order to give the wav files the proper filenames. To record your own voice-over you'll need some method for recording your voice as a wav file. Windows comes with a basic sound-recording program but other more sophisticated programs are available free for download as well. The wav file must be recorded in or converted to PCM 24 khz 16 bit mono format, otherwise the process will fail and an error message will be displayed in the log.
Real vo needs to be stored in ~installpath~\Dragon Age\addins\[moduleuid]\module\override\toolsetexport\[lineid]_m.wav - you can dump wav files anywhere under the toolsetexport directory and they will be picked up but for organizational purposes you should probably organize it into subfolders grouped by conversation.
Placeable sound resources
= Adding sounds to animations
The Blend tree editor allows sound events to be associated with an animation's timeline. So for example, an animation of a golem clapping could have a clanging sound added to the moment of impact of its hands.
Soundsets for characters (the collection of lines they choose from in combat and other routine in-game activities) are created as conversation resources, and are associated with individual creatures via a character resource. This allows one soundset to be reused for multiple different creatures.