摘要
本文以《樂府詩集》所載唐人舊題樂府詩為核心，考述詩歌外圍的相關文獻，探析詩作本身的繼承、新變傾向，突出唐人舊題樂府的創作成就，希望為近年臺灣學界在唐人舊題樂府研究上相對滯後的情況有所建樹。
全文分上下二篇，上篇描繪樂府舊題曲調的發展脈絡、架構唐人舊題樂府創作的音樂背景、探討唐人舊題樂府的音樂體性，下篇解讀、歸納千餘首唐人舊題樂在命題方式與內容上的特點，繪製表格總覽其詳，最後整合上、下篇的研究成果，提出可靠且具有新意的論點。
上篇共分四章，第一章，論述了唐人舊題樂府的名義。本文定義唐人舊題樂府為：唐人取先唐樂府舊題所造之詩，該樂府舊題曲調隸屬華樂系統。
第二、三章，交代了魏晉以來至於隋唐的音樂發展，音樂品種的相關史料外，也透過歷朝音樂官署的建置、興廢，側面補充說明由相和歌而清商舊曲而清商新聲而清樂的遷衍軌跡，並對李唐多元而發達的音樂文化加以著墨。
第四章，整理唐代以來涉及唐人舊題樂府入樂問題的正、反面資料，辯證、修訂吳相洲先生在這論題上的開新之見。
下篇亦分四章，對唐人舊題樂府進行分類研究，考察詩作命題上的沿襲或衍生，作品在內容主題上的繼承和新變。第一章，研討唐人鼓吹、橫吹曲辭，第二章，聚焦唐人相和、清商部類的舊題樂府，第三章，探析唐人琴曲、舞曲歌辭，第四章，交代唐人雜曲歌辭的復變表現，並綜合上下篇相互關涉的要點，強調舊題曲調僅僅是唐人舊題樂府的創作背景之一，不應從某舊題曲調傳唱於唐，直接推斷同題唐人擬作入樂可歌。
經由上下二篇的研究，本論文對前人成說的修定與獲致的「新」得如下：
第一，兩漢的樂府詩，郭氏稱作「古辭」，但《樂府詩集》中所謂「古辭」未必特指漢謳，也用以泛稱曹魏之前年代古早的詩文。
第二，清商曲辭共分「吳聲歌曲」、「西曲歌」與「江南弄」三類，＜神弦歌＞、＜上雲樂＞和＜雅歌＞只是子目，大陸學者以之並舉為六的成說，本文根據《樂府詩集》的編輯體例加以釐正。
第三，從《樂府詩集》的立場來看，吳歌、西曲曲式的特點有三：一是吳聲歌曲的引子或尾聲僅稱作「送」，與西曲歌有別。二是西曲歌裏具舞曲性質者，只有「和」聲而無「送」聲。三是只有非舞曲的西曲歌，才有「送」聲、「和」聲並用的情況，但何者在前何者居後則難以斷言。
第四，在唐人舊題樂府創作音樂背景方面，考見「初唐所傳清樂，歌曲多於舞曲，曲調以清商新聲為大宗」。此外，還原天寶元年以後，祭祀老子的儀典先後演奏＜混成＞、＜太一＞以降神、送神的實際情況，糾正「天寶元年，定玄宗的廟樂」的誤說。
第五，本文認為「舊題樂府入樂材料」所傳達舊題曲調流播訊息當區隔為二：一是先唐舊曲舊辭傳唱當時，非關唐人舊題樂府創作。二是唐人所造舊題樂府搭配舊曲歌唱。承此，唐人舊題樂府在音樂表現上可能的情形有三：
一、舊題曲調流傳，唐人作舊題以入樂。
二、舊題曲調流傳，唐人作舊題不入樂。
三、舊題曲調或存或亡，唐人所作舊題樂府配入當時新興曲調。
第六，唐人舊題樂府在內容主題上繼承較新變多，但仍呈現復變交織的面目，命題之際，沿襲舊題或另有創制皆有而以前者為常。
此外，唐人琴曲歌辭與清商曲辭的內容，較少寄寓詩人主觀情志，多屬模擬、繼承，這與琴曲自身的封閉性、清商新聲去唐未遠而多行於當時，相應的歌辭受其音樂背景制約較大有關。以上都是對唐人舊題樂府研究可茲補充的論說。
關鍵詞：古題樂府、曲調源流、舊題曲調、音樂、清商、雅樂、擬變、復變

Abstract
This research is based on the old Yue Fu poetry recorded in the Yue Fu Poetry Anthology in the Tan Dynasty, using the literature related to the poetry, analyzing the inheritance, transition of the poetry, pointing out the achievement of the old Yue Fu poetry in Tan Dynasty and hoping to give a great devotion in this academic field.
The research can be divided into two parts: the first portion depicts the development of the melody of the old Yue Fu, the background of the old Yue Fu and the musical characteristics of the old Yue Fu ; the second portion interprets the characteristics of the topic as well as content of thousands of old Yue Fu poetry in Tan Dynasty, and draw tables for them. In the end, the result of these two parts will be combined and the reliable and new ideas will be provided.
The first portion of the research is divided into four chapters: chapter one discusses the name of the old Yue Fu poetry in Tan Dynasty. This research defines the old Yue Fu poetry in Tan Dynasty as: “the old Yue Fu poetry in Tan Dynasty adopted from pre-Tan era, whose old melody belongs to the system of the Hua Xia music.”
Chapter two and three depict the development of music from the Wei Jin Dynasty to the Sui Tang Dynasty, and the historical data of the type of music. Moreover, the establishment and the abolishment of each dynasty’s governmental agency responsible for the oversight and administration of the development of music is described as a supplementary illustration of how the Xianghe ballad was evolved first into Qing Shang old ballad, then Qing Shang new ballad, and eventually Qing ballad. The diversification and the richness of the ballad culture in Li Tang Dynasty are also addressed.
As for chapter four, from age of the Tan Dynasty, the positive and negative data related to the issue of whether the old Yue Fu can be sung or not will be arranged in order to revise and verify Mr. Shiang Jou Wu’s comment on the same issues.
The second part is divided into four chapters on the classification of the old Yue Fu poetry and the history as well as the transition of the topics and content in the poetry. In chapter one, the Guchui and Hengchui ballad in Tang Dynasty will be discussed. Chapter two deals with the old Yue Fu of Xianghe ballad and Qingshang music in Tang Dynasty. Chapter three is on the Lyrics of Guqin and Dancing Songs. Chapter four focuses on the change of the Zaqu ballads in Tang Dynasty. Based on the findings of the first and second parts, the author points out that the old melody was just one of the many source materials that inspired the formation of the old Yue Fu in Tang Dynasty; it would be wrong to assume that a rhyme written during Tan would also be a song simple because it has the same title (name) with an old song still popular then.
Based on the findings of the study stated above and the comments of the former scholars, the conclusions of the study are as follows:
1. Guo called the Yue Fu poetry in Eastern and Western Han Dynasty as “Gu Tsz”; however, in the Yue Fu Poetry Anthology, “Gu Tsz”refers to any poetry before the Cao Wei Dynasty; the term does not refer to Han ballads exclusively.
2. Qingshang music consists of“Wu Sheng Ballad”, “Xiqu Song”, “Jiang Nan Song”; “Shen Shian Song”, “Shang Yun Song”, “Ya Song” are just subtitles of them. Yet the Chinese scholars mistakenly regard them as six independent categories indexed at the same level. This research corrects the Chinese scholars’ mistake based on the formatting of Yue Fu Poetry Anthology.
3. Three features are found based on Yue Fu Poetry Anthology:
Different from “Xiqu Song ” the beginning and ending of the “Wu Sheng Ballad” are called “Sung”.
There is no “Sung” sound but “He” sound in “Xiqu Song” that were dance music.
The use of both“Sung” and “He” are found only in“Xiqu Song”that are not dance music. But it is difficult to distinguish the order of the “Sung” and “He”.
4. As for the creation background of the Old Yue Fu in Tan Dynasty, there were more songs than dancing songs in the Qing Song in the early part of Tan Dynasty; besides, the melody stressed on the “Qing Shang new ballad”. Moreover, after Tian Bau Yuan Nian, in the ceremony of the Lao Tzu, the song of“Huen Cheng”is played to summon God, while the song of “Tai Yi” is played to send the god away. Thus, the statement— “in Tian Bau Yuan Nian, the ballad in the Temple is for ding shiuan tzung.” — can be corrected.
Fifth, this research divided the information of the material for the Tang old Yue Fu can be sung or not into two portions: one is that the old melodies and lyrics before the Tan Dynasty is not the creation of the old Yue Fu Dynasty. Another is that people in Tan Dynasty combine the topic of the old Yue Fu with the melody of the old Yue Fu in Tan Dynasty to sing. Thus, the music performance of the old Yue Fu in Tan Dynasty has three characteristics:
First, the old melodies can be sung, people in Tan Dynasty used the old Yue Fu to sing.
Second, the old melodies can be sung,people in Tan Dynasty do not use the old Yue Fu to sing.
Third, regardless of the existence or nonexistence of the old Yue Fu, people in Tan Dynasty combined the old Yue Fu with the new melody in that time.
Last, both the inheritance and transition of the content and topic of the old Yue Fu in Tan Dynasty can be seen. When it comes to name the topic, the old topic is often used.
Besides, the contents of the Lyrics of Guqin Songs and Qingshang ballad in Tan Dynasty do not often reveal the subjective emotion of the poet, but the imitation and inheritance of the content. It is because of the feature of the isolation of the melody and the population of “Qing Shang Shin Sheng”. Thus, the ballad is confined to the rule as well as background of music in that time.The above statements are able to be added to explain the old Yue Fu in Tan Dynasty.