聖樂的目的和該有的特質
我不會在此探討《在善牧職務中》所定出的原則細節，不過會指出羅馬教宗提出的兩個基本原則。
第一個原則闡述了聖樂的目的：它不單是藝術本身，而應當是為神聖禮儀的特定服務而存在的真正藝術。聖碧岳十世教宗宣稱：
「聖樂是禮儀的組成部分，是指向禮儀的總體目標，亦即光榮天主及聖化和啟迪信友。它有助提高教會典禮的美麗和輝煌，而由於它的主要職責是為禮儀文本披上華衣，用合適的旋律呈現給信徒去理解，其目的是使文本更為有效，使得通過這個方法更能激起信眾的虔敬，更好地聚積他們來自神聖奧秘慶典的恩寵果實。」
聖碧岳十世教宗以明確態度指明了，為神聖禮儀譜寫音樂的藝術家有甚麼是必須常常放在心靈的首要位置，也就是光榮天主和啟迪願意崇拜天主的信友成聖。接著自然是準備譜寫聖樂的音樂家，務必把自己全然謙卑地躬身為神聖禮儀的經文服務。他的音樂應當為神聖經文和它們所宣告的現實有更深層益處的服務。
第二個原則闡明聖樂該有的特質——聖潔、美麗和普世性。 教宗描述了每種特質。聖潔意味著聖樂應當「避免一切世俗的事物，無論是它本身或它的表演方式」。換言之，為敬拜天主而譜寫音樂的藝術家有需要淨化樂譜以去除任何與天主聖潔不相關的事，以及淨化表演本身任何與天主聖殿相異之物。 聖樂的美麗是指，聖樂「必須是一門藝術。因為沒有其他的方式，可以使聽眾在心裡產生教會希望在她的禮儀中使用聲音的藝術所達至的效果」。聖樂的特殊要求絕不表示某種音樂藝術的形式是劣質或比其他的次等，而是有一種音樂藝術形式能提升到最高水平，通過神聖禮儀，為天主與人的特殊相遇服務。因此，用作敬禮天主的音樂，應奮力成為該段時期的最佳音樂。
最後，對於聖樂的普世性，「雖然每個國家可採用屬於民族風格的任何特形式於其教會音樂中，但它要求這些形式必須順服於聖樂的獨特本質，使得它永不會在任何陌生聽眾心中產生不良印象」。適合於特定地域的音樂或許能夠為聖樂發展提供養分，但只有當它能尊重聖樂的獨特本質，且具備必要的聖潔、美麗和普世性的特質，才能做到。任何特別形式的聖樂確實要輕易地在普世教會為神聖敬禮的音樂體系中找到其位置。
【文本來源：雷蒙德•良•伯克樞機 (Raymond Leo Cardinal BURKE) - 我要永遠歌頌上主： 天主教聖樂簡史 pp.2-4】
The Purposes And Qualities Of Sacred Music
Without entering into the details of the discipline set forth in "Tra le sollecitudini", I note the two general principles set forth by the Roman Pontiff.
The first principle sets forth the purposes of sacred music, which cannot be an art in itself but rather must be true art at the specific service of the Sacred Liturgy. Pope Saint Pius X declares:
"Sacred music, being an integral part of the liturgy, is directed to the general object of the liturgy, namely, the glory of God and the sanctification and edification of the faithful. It helps to increase the beauty and splendor of the ceremonies of the Church, and since its chief duty is to clothe the liturgical text, which is presented to the understanding of the faithful, with suitable melody, its object is to make that text more efficacious, so that the faithful through this means may be the more roused to devotion, and better disposed to gather to themselves the fruits of grace which come from the celebration of the sacred mysteries."
In a clear manner, Pope Saint Pius X indicates what must always be, foremost, in the mind and heart of the artist who composes music for sacred worship, namely, giving glory to God and inspiring holiness in the faithful who desire to offer Him worship. It follows naturally that the musician who sets out to write sacred music must place himself, with all humility, at the service of the texts of the Sacred Liturgy. His music must be at the service of a deeper appropriation of the sacred texts and of the realities which they announce.
The second principle sets forth the qualities which necessarily mark sacred music, namely, holiness, beauty and universality. The Holy Father describes each quality. Holiness means that sacred music must "avoid everything that is secular, both in itself and in the way it is performed." In other words, the artist who writes music for the worship of God must purify both the musical score itself of anything which is not coherent with the holiness of God and the performance itself of anything which is foreign to the House of God.
Beauty means that sacred music "must be an art, since in no other way can it have on the mind of those who hear it that effect which the Church desires in using in her liturgy the art of sound." The particular demands of sacred music, in no way, indicate a form of musical art which is inferior or compromised, but rather a form of musical art elevated to the highest possible level, to the service of the privileged encounter of God with man through the Sacred Liturgy. The music employed in the worship of God must, therefore, strive to be the best music of the period.
Finally, the universality of sacred music demands that "although each country may use in its ecclesiastical music whatever special forms may belong to its own national style, these forms must be subject to the proper nature of sacred music, so that it may never produce a bad impression on the mind of any stranger who may hear it.?' While the music proper to a particular region may be able to offer something to the development of sacred music, it can only do so when it respects the distinct nature of sacred music and is marked by its necessary qualities of holiness, beauty and universality. Any particular form of sacred music must indeed easily find its place within the body of the universal Church's music for sacred worship.
[Source: Raymond Leo Cardinal BURKE - Aurelio Porfiri：Forever I Will Sing, A Short History of Catholic Sacred Music, pp.3-6]