muteTrack ({ state, dispatch, commit }, track) {
      const trackData = state.tracks[track]
      if (!trackData) {
        throw new Error('Invalid track specified')
      }

      const mutes = Array.from(trackData.keys())
        .map(id => dispatch('muteSound', id))

      commit('setMute', { track, muted: true })
      return Promise.all(mutes)
    }
Mutes a track regardless of current mute state.  Maintains volume
settings on sounds.

@param track {string} track to mute

@return Array of sound IDs that were muted

@throws {Error} when invalid track specified