If you want to listen for alsa mixer changes you can try scripting around `amixer events`. It seems to be undocumented but works.
- [dev] My dwmstatusbar.c Mariano Bono
- Re: [dev] My dwmstatusbar.c Comrade DOS
- Re: [dev] My dwmstatusbar.c Krol, Willem van de
- Re: [dev] My dwmstatusbar.c Adrian Sadłocha
- Re: [dev] My dwmstatusbar.c Mariano Bono
- Re: [dev] My dwmstatusbar.c Krol, Willem van de
- Re: [dev] My dwmstatusbar.c Rob
- Re: [dev] My dwmstatusbar.c Galos, David
- Re: [dev] My dwmstatusbar.c Bryan Bennett
- Re: [dev] My dwmstatusbar.c Michał Kazior