This is, I think, the best version on YouTube. The song itself is about six and half minutes long. In this clip, the song itself doesn't start until just before the one minute mark. It goes for about three minutes and all the rest, half the song, is that long coda. So, structurally, this poses no more challenge to a listener than any other pop song.
But longer classical pieces are usually more structurally complex than shorter ones. Basically a composer writes a longer piece because the material requires or justifies it. This is even true of some minimalist pieces. While In C by Terry Riley could go on forever with the most minimal of material, pieces by Steve Reich usually have their length dictated by the musical processes they involve.
What are we calling a "long piece" anyway? In my second post on medium length pieces the two examples I chose were six and seven minutes long. I would call anything from around six minutes to around ten or twelve minutes medium length, I suppose. With very few exceptions, there are no single movements longer than this until we get into the later eighteenth century.
That phrase "single movements" brings up another challenge to the listener: classical music very often comes in the form of multi-movement pieces. We will talk about that in some detail, but first I want to talk about one kind of piece that can be quite long, but is not like other multi-movement pieces: this is the theme and variations.
The theme and variations form is really the first way composers discovered how to write longer pieces. One of those exceptions I mentioned is the famous Chaconne by J. S. Bach, the longest single movement of the Baroque era. I wrote a whole post on this piece here that I encourage you to read. The piece is about thirteen or fourteen minutes long in most performances, so it definitely qualifies as "long". It is also the last movement of a suite for solo violin and is almost as long as all the other movements put together. How was it possible for Bach to create a structure able to support this length of music? The answer is through variation form. The theme is an eight measure phrase that he simply keeps repeating while varying the melody, rhythm and texture. The harmony itself remains the same until two-thirds of the way through where he moves from D minor to D major for several variations before returning to D minor for the final few variations. The piece is therefore a kind of hybrid of variation form and ternary form.
Most variation-form pieces are presented as a lot of short movements, each based on the theme, rather than one long single movement as in the Chaconne. The most famous stand-alone variation piece in the Baroque is also by Bach, his Goldberg Variations. I did a big post on this piece here that I encourage you to look at. This really is a long piece, about seventy minutes if you do all the repeats, but it comes in the form of a theme, thirty variations and then the theme again. Most of the variations are around two minutes long and they are presented as separate movements--that is, there is a brief pause in between.
Another way the Baroque found to extend the length of a movement was through ritornello form. This is a kind of expansion of ternary form. Where the structure there is a simple ABA, in a ritornello the A keeps returning but in between are contrasting sections so the result is ABACADA, for example. The ritornello section itself can come in the form of short, detachable phrases that can be used in the contrasting sections, which function a bit like a development. The ritornello also can reappear in partial form, so there is a lot of flexibility. However, most examples of the form, which was used to construct most first movements in the Baroque concerto, don't go much over seven minutes long. Here is an example by Bach, the Concerto for Harpsichord and Strings in D major, BWV 1054.
Well that didn't turn out quite as I had planned! I didn't quite get to covering many long pieces! Looks like there is lots left to talk about next time when I will get into what happened in the Classical era to increase the length of single movements.