Selecting native source
There are fixed number of native sources waiting at the native side to play. You can get a specific one you want with NativeAudio.GetNativeSource(_).
This page suggests some strategies to make use of limited native sources.
Exclusive channel
It is not uncommon for a rhythm game to have only few kinds of response sound and is still fun. Taiko no Tatsujin has only 2 kind of response sound for center hit and rim hit. Imagine using Native Audio to make it, it make sense to permanently assign one sound to native source 0 and another sound to native source 1.
The next play of the same kind will cut off previous one however (it maybe desired to reduce audio clutters), you can try alternating 2 sources each instead. e.g. center hit 0 1 0 1 0 ..., rim hit 2 3 2 3 2 ....
Pause and loop
Specifying the source explicitly is important in the case that you have used pause or looping functionality. If new audio lands on the native source that was paused, then the state will disappear. Imagine like in Unity, you also cannot just play all audio into one AudioSource blindly. (Unless you use PlayOneShot which is magical.)
Audio de-cluttering
You can use native source limitation creatively. When playing a rapid gunshot sound you might want the new shot to cut off the old shot's release tail so that the sound is not overcrowded. In that case just use the same native source index over and over.
There are cases where cutoff is natural. For example drum kit's cymbal. A new cymbal hit cutting off the previous one sounds more like a real thing.
A mix of exclusive channel and round-robin
If you use the lazy NativeAudio.GetNativeSourceAuto(), each play will cycle through all sources in round-robin. In the case of allocated 7 sources, it would sounds strange if a snare roll that goes quickly more than 7 times ended up cutting off lingering cymbal, for example.
So here is an example of mixed strategy that may produce better result :
- Cymbals : only
0 - Snares :
1,2round-robin - Toms, rides, kicks, any others :
3,4,5,6round-robin
Snares was given its exclusive round-robin range because it has a longer release envelope, the sound tail being cut off abruptly will be too obvious if only a single native source is allowed for it.
Tip
You can implement your source selection logic in your custom class that implements INativeSourceSelector, then use the NativeAudio.GetNativeSource(INativeSourceSelector) overload.