What appears to be an omission, though, is actually an intentional constraint that was placed upon this book. It only contains musical settings for the Entrance, Offertory, and Communion Antiphons for Sundays and Feasts, and nothing more.
So when it comes to the Responsorial Psalm, the Alleluia and its verse (both of which also form part of the proper), and those other particular chants and antiphons that are found in the Missal for special liturgies, such as those of Holy Week, you have to look to other sources.
The Roman Missal contains the English texts of the antiphons that are prescribed to be sung during the washing of feet for Holy Thursday, but it gives no musical setting for them. The official musical settings for these are to be found in the Graduale Romanum, but these settings are in Latin only.
The following simple chant antiphons may be freely downloaded by parishes that wish to sing these antiphons in English, according to the new translation of the Roman Missal:
These settings take the original Gregorian chants of the Graduale Romanum as their model, yet are somewhat simplified, and attempt to treat the English text in the manner that the Gregorian composers would have treated Latin texts.
These settings are a precursor to the forthcoming choir and cantor companion volume to the Lumen Christi Missal. This companion volume will give the choir what they need while the LCM only gives the people in the pew what they need.
Until this companion volume is completed and becomes available, these and similar cantor scores can be downloaded freely at the Illuminare Publications website under "Free Downloads".