"He has made some valuable discoveries, particularly in reference to certain peculiarities of Beethoven's notation which significantly alter one's preconceptions of interpretation of this and other composers" Sir Charles Mackerras
A Brief Outline of an important issue encountered in the Beethoven Symphonies:
The following examples from the autograph manuscript of Beethoven Symphony No. 7 illustrate how concerned Beethoven was about articulation and note lengths. Until very recently published scores and parts of the symphonies have been inaccurate on this point: "Striche" having been transposed to "Punkte" almost without exception. Even the exact placing of these markings has usually been wrong in the past, a typical example being the following
phrase:
Beethoven Symphony No. 7, 1st. movement, bars 109-113 & bars 114-118
In comparing this example with currently available scores of the Seventh Symphony, one begins to see that the Punkte and Striche have enormous significance, completely transforming one's view of the phrase structure and character. (Beethoven is equally consistent in the recapitulation this theme, and until now published scores have been equally inconsistent!) How important did Beethoven himself view these markings? In his letter to Karl Holtz of August 1825 (quoted in Emily Anderson, The Letters of Beethoven (1961), No. 1421,
Beethoven writes that 
and 
are "not identical". Clearly the difference was of tremendous importance to him. If we agree that the Strich is enormously significant, we must be very sure we understand what Beethoven meant by it. In the future the sources needed to help one reach a decision will be instantly available. Here is an example of the kind of detective work all musicians will soon be able to undertake from the comfort of their own workstation! Firstly, what did the 
mean to the generation preceding Beethoven? What would young Beethoven been taught by his father? Leopold Mozart would probably be one of the first sources one would turn to. In his treatise of 1756,
Leopold writes:
A composer often writes notes which he wishes to be played each with a strongly accented stroke and separated one from another. In such cases he signifies the kind of bowing by means of little strokes which he writes over or under the notes. For example:
(Leopold Mozart "A Treatise on the Fundamental Principles of Violin Playing" English translation by Editha Knocker page 47) This is generally how todays string player would interpret Striche. However, later in the book, in chapter 7 he writes:
Consecutive and continuous rapid notes are subject to many variations. I will here set down a single passage from the first can be played quite smoothly and easily, and in which each note may be performed with its own separate stroke. Great pains must be taken with their exact equality, and the first note of each crotchet must be marked with a vigour which inspires the whole performance. For example:
Now if you wish to accustom yourself to a really long stroke of the bow; if you wish to learn to play notes in one bow, with expression, clarity, and evenness, and therefore make yourself really master of your bow, you can play with great profit this whole passage first in an up stroke, then in a down stroke. But do not forget to apply on the first note of each crotchet the emphasis which must distinguish one crotchet clearly from the other. This is the eleventh variation.
Now when you are thoroughly practised in slurring so many notes together in one stroke, you must also learn to lift the bow and play several notes detached from each other in one stroke; which gives a twelvth variation. For example:
In these four examples we see the Strich denoting accent and separation in example1, emphasis without separaton in examples 2 and 3, and then in example 4 something completely different: an off the string stroke which by definition would need a degree of lightness to make it work. Clearly there is far more to this sign than meets the eye...
At this point one could turn to a source by an important contemporary of Beethoven. The Violinschule by Spohr. Spohr is a vitally important source: he was a close associate of Beethoven and participated in many first performances of Beethoven's works. Again, Spohr echoes Leopold Mozart: this sign has a variety of meanings:
On p.38 of his Violinschule Spohr writes:
"The dashes which in slower music signify the notes are to be short and marked, denote, as used in the following Exercise, that separate strokes are intended, in distinction to slurs." (Ludwig Spohr, Violinschule, (Cassel, 1832) English edition by Henry Holmes)
So far the sign has meant: "marcato," or accented staccato, an accent under a slur, lifted staccato, a simple detached as opposed to a slurred stroke, and here:
The fact that 
has a different meaning to 
is emphasised later: Spohr uses staccato dots as we know them today a) to separate notes in the same bow (portato), and b) to indicate spiccato, or "staccato leggiero" as he calls it.
Leopold Mozart only uses dots in one context: under a slur to indicate "portato" bowing:
It happens also that under the circle or, if the circle be under the notes, over the same, dots are written under or over the notes. This signifies that the notes lying within the slur are not only to be played in one bow-stroke, but must be separated from each other by a slight pressure of the bow. For example:
This is precisely how Beethoven uses dots in the 7th symphony: the second movement provides a particularly clear illustration of the juxtaposition of dots and dashes:
Autograph eg 2
Beethoven Symphony No. 7 2nd movement, bars 17-24
These DIFFERENT articulations are vital to the enunciation of the phrase- especially as melody has been dispensed with and only rhythm and harmony are present.
What conclusion can one reach from this preliminary exploration?
A dash often tells one about the importance of a note in the context of other notes: a kind of musical underlining or exclamation mark. Underlining the importance of a note may be acheived by a variety of means: eg. louder, shorter, more accented, (even more sustained on occasion) the most natural and musical means depending on the context in which it is used.
I have come to the conclusion that Beethoven in particular will also use this sign as an indication of balance, marking the leading voice with a method that is very simple, and yet very precise and subtle. Look at any of the recently published urtext editions of the 2nd symphony (eg. 1st movement, bar 61) for examples of this.
In the light of this discussion, one begins to see that we have a huge responsibility to interpret these signs a) accurately ie. only where their use is clearly specified or logically implied and b) musically within the context in which they appear.
As the Strich usually has a structural function: ie. it signifies a note's relative importance to other notes, by misreading it as a dot, ignoring it, or superimposing it where its use was not intended, one can easily subvert the structure of a phrase, or even a whole work. Anyone doubting the importance of this needs only to look at Beethoven's annotations to the set or parts used for the first performance of the seventh symphony (currently in the Gesellschaft der Musikfreunde, Vienna).
Here are two brief examples of the application of this knowledge:
Autograph excerpt 3
Beethoven Symphony No. 7 1st. movement bars 1-4
Here the dash denotes a sweeping, ringing accent, producing pillars of sound which deliniate the two bar phrases. The crotchet lasts about a crotchet: its exact duration and rate of decay defined by the acoustic of the hall. The psychological difference between a staccato dot and a dash is enormous: one takes away duration, the other adds significance.
Incidentally, note the alla breve marking. Without access to this manuscript, Schoenberg writes on p.171 of "Structural Functions of Harmony" (London 1954): "I am convinced that 
= 69 is a misprint. Evidently the two episodes on the mediant and submediant (bars 24-34 and 42-52) have a march like character." He goes on: "Besides, if one of these masters writes sixteenth notes, he means it..." Schoenberg ultimately decided that a tempo of around 
= 52 was the most logical, and came to this conclusion on purely structural grounds. From the same starting point, Gunther Schuller: another probing musical intellect, in his brilliant discussion of the conductor's art "The Compleat Conductor" (Oxford 1997) writes about Schoenberg's "intellectually intriguing idea," on p.233. Access to the autograph score with its alla breve time signature makes Schoenberg's tempo conception even more credible. It is the missing link that means Schoenberg's theory should be taken very seriously indeed.
Here is the second page of the autograph:
Autograph excerpt 4
Beethoven Symphony No. 7 first movement bars 6-10
Note the placing of the dashes, signifying the end of one phrase, and the beginning of the next. Also arguably and indication of balance.
In the following extract, the smattering of dashes in bars 427-429 clearly are intended to be continued throughout this sequence. Here they take on the role of a strong accent: a mere staccato totally looses the sense of syncopation.
Autograph excerpt 5
Beethoven Symphony No. 7, 1st. movement, bars 427-431
There are many, many more examples from this work alone that one could quote to show how free access to original sources is going to change things. I will end this brief outline with one of the most controversial: the end of the second movement has always been a source of disagreement. This is what Beethoven actually wrote:
Autograph excerpt 6
Beethoven 7 2nd. movement (conclusion)
With thanks to the Biblioteka Jagiellonska in Krakov, Poland, for access to the Beethoven manuscript, and to Oxford University Press for permission to quote from Leopold Mozart "Treatise on the Fundamental Principles of Violin Playing"