Rorate Caeli has posted a letter from the Pontifical Commission on Ecclesia Dei addressed to a church choir in the Philippines stating that bishops may not say the "Missa Cantata", only a Low Mass or a Pontifical High Mass, due to the rubrics of the 1962 Missale Romanum.
This decision (although not a Papal Bull with full force of the law) is a blow to the all bishops who say the "Pontifical Sung Mass" as the letter describes, due to the lack of the full amount of sacred ministers in major orders which prevent the chanting of the Epistle by a subdeacon and the Gospel by the deacon when the Bishop is celebrant. Both SSPX and diocesan bishops have to offer the Missa Cantata on these occasions, especially after they administer Confirmation, which the ceremony is chanted and the organ is often played. It's not meus culpus that bishops have to modify their Masses due to the lack of personnel in these dark days.
Yes, Solemn High Mass said by a priest is the original form of Mass, the others are abbreviations. Same with the Pontifical High Mass, but if the bishop is not a cardinal, metropolitan, or the local ordinary, he cannot pontificate from the throne unless he is granted permission or ordains. The Pontifical High Mass at the faldstool (on the Epistle side of the church) is considered an abbreviation and applies to visiting and auxiliary bishops.
The rubrics have always allowed for priests to say the Missa Cantata because most parishes only have one priest. If the modern-day permanent diaconate were a true diaconate every parish would have a Solemn High Mass every Sunday. The same with Bishops, if they actually pontificated every Sunday in their cathedrals then such a question would have never been asked.