The music for the Solemnity of All Saints is absolutely wonderful. Most of the chant is in Mode I and nicked from other feasts (with the exception of the Alleluia) but who cares. It is all fantastic. If you have never sung an Introit before, you have to sing the Gaudeamus. It is one of my favourite chants and has that instantly recognisable Mode I formula, that is you may recognise from Suscepimus Deus, the Introit for Candlemas or the Ave Maria Offertory Antiphon.
Ted Krasnicki has written an excellent commentary on all the chants of All Saints. This is a PDF saints_properscommentary
Head to Jogues Chant to hear a recording of the Gaudeamus.
Another great piece to sing is the Vespers Hymn for All Saints, Christe Redemptor Omnium found in the Liber Hymnarius on P.460. In the Roman breviary this is sung to the text Placare Christe servulis. If you are wondering why the same tune has two quite different texts then head to HERE for an explanation and a translation. Mass is in the ordinary form at our parish this evening so will be singing the Christe Redemptor text.
I found on the internet yesterday. the organ accompaniment for Placare Christe sérvulis.
Finally, there is the Litany of the Saints. This can be sung as an entrance chant or in place of the usual Penitential Rite. You will find it in the Liber Usualis page 756 or in the Graduale Romanum at the Easter Vigil.
I have found a PDF on Musica Sacra in a good format. Litany of Saints _Ordination_-2
There’s lots of good recordings on the internet, just be careful you don’t just type in ALL SAINTS or otherwise you might find yourself singing this.