If I’ve missed one, please feel free to add; please list only one, maybe two or three at most for each selected category; and an illustrative link(s) is requested, but not necessary. Thanks.
1) Gregorian Chants(or other earlier forms of Church or Secular music)
2) Toccata/Passacaglia/Variations or any used predominantly in the Baroque and Rocco periods
3) Chamber ensembles – any combinations of instruments(any periods)
4) Choral: Chorale/Cantata/Oratorio/Mass, etc.
5) Vocal(lieder) solo; or duet, trio, quartet, etc.
6) Symphony(symphonic)
7) Concerto(for any instrument)
Instrumental solo
9) Opera
10) Ballet(suites, or individual selection(s))
11) Concert Overtures(or operatic, incidental music, etc.)
12) Any I’ve missed? FREE form? A cappella?
Have fun,
Alberich
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The first responder "MissLimLam", stated that she thought that she probably misinterpreted the question.
No, my fault; it needs ALTERATION & CLARIFICATION:
Please choose from no more than a maximum of 4 of each listest category, as your prefered forms.
And choose only one representative selection for each form chosen; illustrative links are requested, but no necessary. Thanks.
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Thanks to all who have responded. Looks like I’ve made the biggest blunder so far in my career on this forum; I forgot to include the most important form of all in the optional categories:
the SONATA – mystified why no one hasn’t noticed it.
"hahu077": sorry about the omitted 3rd "o" in Rococo.
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Oh Dear! Another one of those instances in which there is no clear cut Best Answer for me; sorry for the cop-out, but I just can’t: "great answers" all.
that missing "o" in ROCOCO can lead to misunderstandings 
i simply can’t decide which form i like best (i like them all, maybe all but the Gregorian chants). it can change very fast and it’s depending on my mood.
btw, i had a very funny experience yesterday. i came across the word "toroimeray" and thought "wtf does that mean?". fortunately i spelled it out loud and thanks to my german knowledges it fell like scales from my eyes and it turned out to be Träumerei (by Schumann).
correct spelling is the half life 
added
ok, 4 forms and 1 example
Oratorio
Messiah by G.F. Handel (especially the Hallelujah)
Symphony
No.5 by Beethoven (4th movement)
Concerto
Piano Concerto in A minor by Grieg (1st mvt.)
Ballet
Nutcracker by Tchaikovsky (march)
I have probably misinterpreted your question… and I am unable to answer completely at the moment, but I love concerti and opera.
My favourite concerto is Vivaldis concerto for Lute in D major:
http://www.youtube.com/watch?v=lF4GKIILF_U
and my favourite opera is:
http://www.youtube.com/watch?v=qVZNx39xYiA
Alberich I will add to this tomorrow, but at the moment I cannot. Forgive me.
References :
Hmm, I think I’m going to have to think extremely carefully and meticulously about my answer.
I can’t neglect the Piano; it is my favourite instrument and I always love to play it.
Piano Solo:
Liszt – Sonata in B Minor:
Part 1 – http://www.youtube.com/watch?v=vCF8C5U7Pco
Part 2 – http://www.youtube.com/watch?v=CD0m9vfXadQ
Part 3 – http://www.youtube.com/watch?v=atRAhucAoLU
Part 4 – http://www.youtube.com/watch?v=E0sgkllWzbQ
I absolutely adore this Sonata, though I doubt I will ever play it as masterfully as Kissin. The second movement is beautiful and although Brahms decided to sleep the composition out, I think the themes incorporated into this Sonata are fantastic.
Of course, I do love Concerto (For any instrument) but I feel compelled to restrict my choice to one form.
Thank you Alberich, another insightful question.
References :
that missing "o" in ROCOCO can lead to misunderstandings
i simply can’t decide which form i like best (i like them all, maybe all but the Gregorian chants). it can change very fast and it’s depending on my mood.
btw, i had a very funny experience yesterday. i came across the word "toroimeray" and thought "wtf does that mean?". fortunately i spelled it out loud and thanks to my german knowledges it fell like scales from my eyes and it turned out to be Träumerei (by Schumann).
correct spelling is the half life
added
ok, 4 forms and 1 example
Oratorio
Messiah by G.F. Handel (especially the Hallelujah)
Symphony
No.5 by Beethoven (4th movement)
Concerto
Piano Concerto in A minor by Grieg (1st mvt.)
Ballet
Nutcracker by Tchaikovsky (march)
References :
So many choices!
My 1st favourite would be Opera. As you know, I am a great fan of Wagner so I guess it’s pretty obvious as to why I chose Opera as my favourite.
I don’t know why I’m bothering with a link because I’m sure you know the whole thing off by heart! Here it is anyways.
Der Ring des Nibelungen, Das Rheingold Act 1: Prelude-Part I: http://www.youtube.com/watch?v=wiyoLa9z1ao&feature=related
My second favourite would be the concerto. The concertos of Beethoven, Tchaikovsky, Mozart and Shostakovich all make me want to jump up and down with glee.
Here is a selection from my No.1 favourite concerto:
http://www.youtube.com/watch?v=Yk-D5VtfzEA
And my 3rd choice is the Concert Overture. I love these. I love the way that they tell a story.
Here is one of my favourites (a cliche one, but still, I love it):
http://www.youtube.com/watch?v=yE34mKmizY8
Thanks so much Alberich for this fun question!
References :
1. Opera
http://www.youtube.com/watch?v=PuA1p_sbdEg&feature=related
2. Symphony Orchestra
http://www.youtube.com/watch?v=FFltqVS8d9I&feature=related
3. Piano Solo
http://www.youtube.com/watch?v=FFltqVS8d9I&feature=related
Note, for me the categories have remained the same for a life time
but I am still learning and adding new music all the time, the choices from youtube were convenient examples rather that definitive performances. Thank you Evas
References :
Hello, Alberich
Like some others have said (sorry – I suppose variety would be more interesting for you, but this choice is undeniable for me), I would have to choose the form of piano solo as my favorite.
Of course, the other eleven categories are all wonderful, and can at times be even preferable to the solo piano. But I find that, in the moments that I turn to music for comfort, the pureness and expressiveness of the sound of the lone piano just cannot be surpassed. If there were angels somewhere out in the universe, which I don’t believe (but of course, I could be wrong), I just have to imagine that the sound coming from them would not be an ethereal human voice but the voice of the piano.
At the moment, a piece I find myself attracted to is Scriabin’s "Vers La Flamme," Op, 72. It’s dark yet fulfilling, it really consumes the mind. I think it is a good example of how the piano can capture you and take you to a new place…
http://www.youtube.com/watch?v=82DKeZXpSmI
My computer doesn’t seem to want to cooperate in making the links blue and clickable, but copying and pasting the link into your search bar should work. Or, if it doesn’t, you can just search the piece on youtube. It wasn’t hard to find!
Take care,
Mina
References :
Instrumental solo. Specifically piano music.
Among my favorite compositions are the fugue movement from Beethoven’s Sonata no.29 "Hammerklavier"
http://www.youtube.com/watch?v=XQLBAQ-AKU4
Scriabin’s Sonata no.5
http://www.youtube.com/watch?v=I0lfk2QgPhc
Prokofiev’s toccata op.11
http://www.youtube.com/watch?v=bSPDmQtWPak
Liszt-Mephisto Waltz no.3
http://www.youtube.com/watch?v=WgLSJHfvCrM
References :
2) Toccata/Passacaglia/Variations
– Bach’s "Ciacconna" from the 2nd Partita for Unaccompanied Violin
http://www.youtube.com/watch?v=RtLw91Ggwuk
3) Chamber ensembles
There are too many to list, but I’ll just give a few of my favorites that come to mind:
– Mendelssohn’s String Octet in Eb Major – http://www.youtube.com/watch?v=GnjVbn8HqF0#t=0m52s
– Ravel’s String Quartet in F major, 2nd movement – http://www.youtube.com/watch?v=CBy4f5DE-yk
– Janacek’s First String Quartet: http://www.youtube.com/watch?v=SgvWJHzsYRE#t=0m36s
– Sibelius’ Piano Quintet (a rare piece – no recording on youtube)
6) Symphony (symphonic)
Again, there are too many.
– Sibelius’ Tone Poems "Pohjola’s Daughter" and "En Saga"
http://www.youtube.com/watch?v=ZtB0ZRKSnLs and http://www.youtube.com/watch?v=wC2vbBDqLpg (not a great recording, but the only full one i could find on youtube)
– Walton’s First Symphony
– Rachmaninoff’s Symphonic Dances (http://www.youtube.com/watch?v=E3bbfZHGIMM)
– Philip Glass’ Eighth Symphony (fairly new, no recording on youtube)
References :
There are a few other forms for which I suggest new terms:
Beethoven wrote an Ecossaise in which the even-numbered 16-measure sections are exactly the same but the odd-numbered 16-measure sections are all different.
I would call this either the Canada form or the Bahama form.
And what if the beginning, ending, and all other-odd numbered sections are the same but all other sections are different?
This is what we usually find in a Baroque rondo, such as the Bach E major gavotte for unaccompanied violin.
This is also what we find in Siegfried’s funeral march.
I would call this the Alabama form.
In Pictures in an Exhibition, the opening theme recurs four more times as a link, but does not recur at the end.
I would call this the avatar form.
References :