Maybe, maybe not.
The term 'actuosa participatio' REALLY means "actual" or "real" participation--and as has been argued by highly-credentialed liturgists, this begins internally, with a 'metanoia' or conversion, of oneself to a conformity with Christ.
This metanoia does not necessarily require activity, song, or verbal response.
Thus, art song which is religious and not merely a vehicle for "performance" is perfectly acceptable.
Again, context counts. One solo, done without excessive melodrama or vocal floridity, is not a violation of liturgical norms, IMHO.
Not trying to score points off you, but maybe this is a good time to review the historical record. I suspect a lot of Catholics, like me, have been reading up on the Liturgical Movement in recent weeks.
Mediator Dei is quite plain on the subject of participation:
105. Therefore, they are to be praised who, with the idea of getting the Christian people to take part more easily and more fruitfully in the Mass, strive to make them familiar with the "Roman Missal," so that the faithful, united with the priest, may pray together in the very words and sentiments of the Church. They also are to be commended who strive to make the liturgy even in an external way a sacred act in which all who are present may share. This can be done in more than one way, when, for instance, the whole congregation, in accordance with the rules of the liturgy, either answer the priest in an orderly and fitting manner, or sing hymns suitable to the different parts of the Mass, or do both, or finally in high Masses when they answer the prayers of the minister of Jesus Christ and also sing the liturgical chant.
In addition:
Pope St. Pius X: “Don’t pray at Holy Mass, but pray the Holy Mass...If you wish to hear Mass as it should be heard, you must follow with eye, heart, and lips all that happens on the altar. Further, you must pray with the priest the holy words said by him in the Name of Christ and which Christ says by him. You have to associate your heart with the holy feelings which are contained in these words and in this manner you ought to follow all that happens at the altar. When acting in this way, you have prayed Holy Mass.”
Pope Pius XII: “Place the missal in the hands of the faithful so that they may take part more easily and more fruitfully in the Mass; and that the faithful, united with the priest, may pray together in the very words and sentiments of the Church.”
According to my St. Andew Daily Missal (published in 1937):
"How the faithful can take an active part in this Sacrifice...
"4. To these three ways of interior or spiritual participation, which can be practiced at every Mass, we should, as far as circumstances allow, add exterior or material participation, which may consist: in reading liturgical prayers with the priest, in singing congregatonal and Gregorian chant at High Mass, in responding aloud at Low Mass, and, best of all, in receiving Holy Communion witht the priest during Mass. In this way, we shall draw plentiful fresh draughts of the true Christian spirit at its source, as Pius X wished.
"Certain texts of the Mass are reserved to the priest, and should never be said aloud by the faithful: we can still make these parts our own, not by a mechanical repetition but by reverent and serious reflection, corresponding to the thoughts expressed by these prayers.
"Other parts of the Mass were originally and are still meant to be said by the people: They are of two kinds: those that are to be chanted by the congregation at High Mass, and those that are responded by the ministers, or by the server at Low Mass, on our behalf.
"A first degree of 'Missa dialogata' consists in responding aloud with the server. A second degree (which deserves properly the name 'Missa recitata') adds to the first degree the recitation with the celebrant of all the prayers which are sung by the people at Missa Cantata, the Gloria (Et in terra, etc.), the Credo (Patrem omnipotentem, etc.), the Sanctus, and the Agnus Dei. (1)
"Before Holy Communion we should say not only the Confiteor with the server, but the Domine, non sum dignus, which the priest says at that moment on our behalf, may also be said three times with him."
"(1) The lawfulness of this use is henceforth beyond any doubt..It has been expressly authorised, recommended, or even put into practice in the first or second degree by the bishops of different countries, and it is most favourably regarded by Rome."