The current Git master looks very broken, segfaulting immediately.
It seems to be caused by commit 27f4a85a95 ("pcm: direct - move the direct struct init to _snd_pcm_direct_new()")
Here's the trace:
$ aplay -D plug:master testing.wav
Program received signal SIGSEGV, Segmentation fault. 0x00007ffff7f14ea6 in snd_pcm_dmix_open (pcmp=0x7fffffffe170, name=0x0, opts=0x7fffffffdef0, params=0x7fffffffdf30, root=0x43b1e0, sconf=0x455ae0, stream=SND_PCM_STREAM_PLAYBACK, mode=0) at pcm_dmix.c:1017 1017 pcm->ops = &snd_pcm_dmix_ops; (gdb) bt #0 0x00007ffff7f14ea6 in snd_pcm_dmix_open (pcmp=0x7fffffffe170, name=0x0, opts=0x7fffffffdef0, params=0x7fffffffdf30, root=0x43b1e0, sconf=0x455ae0, stream=SND_PCM_STREAM_PLAYBACK, mode=0) at pcm_dmix.c:1017 #1 0x00007ffff7f15763 in _snd_pcm_dmix_open (pcmp=0x7fffffffe170, name=0x0, root=0x43b1e0, conf=0x43b620, stream=SND_PCM_STREAM_PLAYBACK, mode=0) at pcm_dmix.c:1374 #2 0x00007ffff7ec72d8 in snd_pcm_open_conf (pcmp=0x7fffffffe170, name=0x0, pcm_root=0x43b1e0, pcm_conf=0x43b620, stream=SND_PCM_STREAM_PLAYBACK, mode=0) at pcm.c:2609 #3 0x00007ffff7ec7a1b in snd1_pcm_open_named_slave (pcmp=0x7fffffffe170, name=0x0, root=0x43b1e0, conf=0x43b620, stream=SND_PCM_STREAM_PLAYBACK, mode=0, parent_conf=0x43c390) at pcm.c:2823 #4 0x00007ffff7ee38a3 in snd_pcm_open_slave (pcmp=0x7fffffffe170, root=0x43b1e0, conf=0x43b620, stream=SND_PCM_STREAM_PLAYBACK, mode=0, parent_conf=0x43c390) at pcm_local.h:1008 #5 0x00007ffff7ee87a3 in _snd_pcm_route_open (pcmp=0x7fffffffe420, name=0x43cc50 "master", root=0x43b1e0, conf=0x43c390, stream=SND_PCM_STREAM_PLAYBACK, mode=0) at pcm_route.c:1367 #6 0x00007ffff7ec72d8 in snd_pcm_open_conf (pcmp=0x7fffffffe420, name=0x43cc50 "master", pcm_root=0x43b1e0, pcm_conf=0x43c390, stream=SND_PCM_STREAM_PLAYBACK, mode=0) at pcm.c:2609 #7 0x00007ffff7ec7547 in snd_pcm_open_noupdate (pcmp=0x7fffffffe420, root=0x43b1e0, name=0x43cc50 "master", stream=SND_PCM_STREAM_PLAYBACK, mode=0, hop=1) at pcm.c:2668 #8 0x00007ffff7ec79f4 in snd1_pcm_open_named_slave (pcmp=0x7fffffffe420, name=0x0, root=0x43b1e0, conf=0x43c320, stream=SND_PCM_STREAM_PLAYBACK, mode=0, parent_conf=0x43d120) at pcm.c:2821 #9 0x00007ffff7ef57ba in snd_pcm_open_slave (pcmp=0x7fffffffe420, root=0x43b1e0, conf=0x43c320, stream=SND_PCM_STREAM_PLAYBACK, mode=0, parent_conf=0x43d120) at pcm_local.h:1008 #10 0x00007ffff7ef824e in _snd_pcm_plug_open (pcmp=0x413768 <handle>, name=0x7fffffffebbb "plug:master", root=0x43b1e0, conf=0x43d120, stream=SND_PCM_STREAM_PLAYBACK, mode=0) at pcm_plug.c:1324 #11 0x00007ffff7ec72d8 in snd_pcm_open_conf (pcmp=0x413768 <handle>, name=0x7fffffffebbb "plug:master", pcm_root=0x43b1e0, pcm_conf=0x43d120, stream=SND_PCM_STREAM_PLAYBACK, mode=0) at pcm.c:2609 #12 0x00007ffff7ec7547 in snd_pcm_open_noupdate (pcmp=0x413768 <handle>, root=0x43b1e0, name=0x7fffffffebbb "plug:master", stream=SND_PCM_STREAM_PLAYBACK, mode=0, hop=0) at pcm.c:2668 #13 0x00007ffff7ec7610 in snd_pcm_open (pcmp=0x413768 <handle>, name=0x7fffffffebbb "plug:master", stream=SND_PCM_STREAM_PLAYBACK, mode=0) at pcm.c:2698 #14 0x00000000004054ab in main (argc=4, argv=0x7fffffffe898) at aplay.c:850