Ah, the terms can get a bit mixed at times so I just wanted to be sure. Anyway...
The 256 source limit in openal soft is more of a soft limit in the software, technically there is no limit beyond what your hardware can handle. Although there are certain reasons why there are limits with things like multiple sounds playing simultaneously, which can overload the system (and the player). According to a few threads [here] and [here] its possible to increase the source limit to whatever you want as a context attribute when creating a context using ALC_MONO_SOURCES and ALC_STEREO_SOURCES.
Generally speaking, in term's of optimization and efficiency its always best to recycle sound players rather than generating them dynamically all the time, or creating a sound player for each and every object as opposed to X number for each object type. For example having X number of sound players for monsters, and then returning and passing them to new monsters as needed rather than just creating more. Such management is typically a result of proximity, as sighted games also feature things like rendering distances and such. In the event that you have X thousand monsters or objects on the screen at once, consolidating distant groups into a single "group" sound, and playing more local near objects with individual sound sources would also work, as near objects may be more relevant.
Put another way: using your example of 4 footstep sounds, a death sound, and some gunshot sounds, do all of those sounds need to play simultaneously? If an enemy dies they don't play footsteps or gunshots, if their firing gunshots they don't play a death sound, or in some cases footsteps either. So in that case, you can assign one sound player to an enemy within range of the player, and load whatever appropriate sounds are required when their required, and switch between them as needed. If/when they move out of range (or die), the assigned sound player can be returned to the queue and wait to be assigned to another monster if needed in range, etc.
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BrushTone v1.3.3: Accessible Paint Tool
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AudiMesh3D v1.0.0: Accessible 3D Model Viewer