auth.js

...

import {setTracks} from '../actions/track';

...

export function auth() {
  return (dispatch) => {
    SoundCloud.connect().then((session) => {
      dispatch(fetchMe(session));
      dispatch(fetchTracks(session));
    });
  }
}

...

function fetchTracks(session) {
  return (dispatch) => {
    fetch(`${API_HOST}/me/activities?limit=20&offset=0&oauth_token=${session.oauth_token}`)
      .then((res) => res.json())
      .then((data) => {
        dispatch(setTracks(data.collection));
      });
  }
}