Just heard back from Father Douglas Martis, author of the Mundelein Psalter. The audio files for the psalm tones and Roman breviary hymns are now back up at the new and improved website of the Mundelein Seminary.
In addition, there is a very special treat for those of us who really want to learn both the psalm tones and to absorb the entire spirit of chanting the office. Go here to find audio files of lauds and vespers for each day of the Triduum and for Easter Day. These are beautiful presentations of the hours done by students of Mundelein's Liturgical Institute. Listen to them and you will hear, put into practice, everything you read in a recently linked article from Sacred Music, including that tiny hush of silence at the end of each line of chant.
Follow along in your own breviary each day of the Triduum and see how quickly you can pick up the chant, even if you don't read a note of music.