There will probably always be people who argue that precision in intonation, diction, tempo, rhythms, etc. is not important. That it is the heart that is most important. While I would agree that the heart of the worshiper is more important then their skill level (good worship but bad music is better than good music but bad worship), I will not concede that precision and excellence are not necessary and proper goals.
Psalms 33:3 says “Sing a new song of praise to Him; play SKILLFULLY on the harp and sing with JOY.” 1 Chronicles 15:22 says “Kenaniah, the head Levite, was chosen as the choir leader because of his skill.”
In Exodus 31 we see the first man the Bibles says was FILLED with the Holy Spirit. The man was named Bezalel and he was a craftsman. An artist/engraver/jeweler. And the Lord filled him with His Spirit to make all the furnishings and fixtures for the tabernacle.
People throughout the Bible are called upon by God to use their gifts and talents for the Lord. But when they use them, they use them with EXCELLENCE. Looking just at the meticulous detail that God gives for the design of his tabernacle and temple, you see that our God loves beauty and excellence. He loves to see us give our best. Because then He can give us the greatest reward. If there were no other argument to be made, there is this: our God is an excellent God. Therefore, He deserves excellent worship.
And our excellence starts with our discipline. Our preparation. Our practicing rudiments. Do not neglect to hone and fine-tune your talents. Just like you stir up your spirit, stir up your talents.