pkg_add: Warning: package `digest-20121220' was built for a platform:
pkg_add: NetBSD/x86_64 6.1.2 (pkg) vs. NetBSD/x86_64 6.1.3 (this host)
pkg_add: Warning: package `libtool-base-2.4.2nb5' was built for a platform:
pkg_add: NetBSD/x86_64 6.1.2 (pkg) vs. NetBSD/x86_64 6.1.3 (this host)
pkg_add: Warning: package `gmake-4.0' was built for a platform:
pkg_add: NetBSD/x86_64 6.1.2 (pkg) vs. NetBSD/x86_64 6.1.3 (this host)
gmake-4.0: registering info file /usr/pkg/info/make.info
pkg_add: Warning: package `pkg-config-0.28' was built for a platform:
pkg_add: NetBSD/x86_64 6.1.2 (pkg) vs. NetBSD/x86_64 6.1.3 (this host)
pkg_add: Warning: package `checkperms-1.11' was built for a platform:
pkg_add: NetBSD/x86_64 6.1.2 (pkg) vs. NetBSD/x86_64 6.1.3 (this host)
pkg_add: Warning: package `alsa-lib-1.0.22' was built for a platform:
pkg_add: NetBSD/x86_64 6.1.2 (pkg) vs. NetBSD/x86_64 6.1.3 (this host)
===========================================================================
$NetBSD: MESSAGE.common,v 1.3 2008/12/18 16:36:11 jmcneill Exp $

This libao package provides its core library but no output plugins
by itself.  You will have to install an audio/libao-* plugin package
in order to get audio working.

  libao-arts    --  aRts plugin
  libao-esound  --  EsounD (ESD or Enlighten Sound Daemon) plugin
  libao-macosx  --  MacOS X plugin
  libao-oss     --  OSS (Open Sound System) plugin
  libao-pulse   --  PulseAudio plugin
  libao-sun     --  Sun audio plugin

Not all are available on every platform.

===========================================================================