Your posts continue to display a massive misunderstanding of the role and ministry of priests.
On weekdays, most priests spend no more than an hour to an hour-and-a-half celebrating Mass, and that's if they have two Masses that day and are accustomed to preaching extensively at daily Masses. On Sundays, it could be up to four hours (three Masses that are longer than daily Masses). Most priests don't sing at all at daily Mass, and even if they sing all the hymns etc. with the microphone on for weekends, they're singing 20 minutes, max, at each Mass. (There are priests who sing the whole Eucharistic Prayer, but they tend to be very good musicians.) In other words, you're focusing on about one hour out of the entire week.
To avoid errors in his homilies, he needs a good grasp of theology (it's surprising how easy it is to say something that's wrong).
What does he do the rest of the time?
1) He hears confessions, for which he needs to know moral theology. It also helps to have at least a basic knowledge of psychology.
2) He meets with people who have spiritual questions. For this, he needs an understanding of the process of spiritual growth, which is intimately connected both with human psychology and with the ways God is accustomed to working with us.
3) He fields calls/emails/message board posts from people who have questions of all sorts. In this current age, some are struggling themselves with issues of faith and reason, and many more have children or friends who are.
Those priests who are in charge of parishes also spend a massive amount of time on adminstrative matters, which are generally left out of the seminary curriculum and learned by observation when a priest begins his ministry as an assistant to an experienced priest.
Hopefully, he finds time to pray in all of this.
The current seminary system was established at the Council of Trent,
Session XXIII, Chapter 11. It replaced hit-or-miss training whose defects were clearly showing in clergy who had been unprepared to deal with the Reformation.
The Second Vatican Council addressed priestly formation in its document
Optatam Totius.
In the United States (I assume other countries have something similar), the concrete norms for seminary training are in the
Program for Priestly Formation (PPF).
Finally, St. John Paul II's great letter
Pastores Dabo Vobis lays out a comprehensive vision of what it is to be a priest in the modern world.
If you want to know why musical training is not on the forefront of priestly formation, and if you want to know what is and why, you need to review these documents. Frankly, if you continue to post the same sort of things you're posting in this thread, it will be a strong indication that you aren't really interested in the answers to your questions, and I (and I expect many others) will cease answering them.