To respond to a thread about unaccompanied horn works (in the horn mailing list), I will make a list of those quality works that I know.  Undoubtedly, there will be some omissions of some favorite.

Range Designations:

C-C below bass clef
c-2nd space c in bass clef
c'-middle c
c''-3rd space c in treble clef
c'''-high c

So here is a partial annotated list:

Adler, S.  Canto 9

-Dedicated to Verne Reynolds, this single movement work has a very reasonable range, ab to bb''.  The first section is rhapsodic with angular leaps.  The second section at first glance does not seem problematic, being basically in 6/8, however there may be insertions of unannounced 4/8, 5/8, 7/8, or 9/8 patterns that are easy to trip over.  Also this work frequently uses bass clef.

Arnold, M.  Fantasy

A very popular work, often found on competition lists.  This is a good selection to pick for a first venture into unaccompanied pieces.  The piece is written in ABA form.  The A section being a jaunty 6/8 theme reminiscent of a sea chanty.  The B section is more pensive and can benefit from much rubato.  A transition passage which features fanfare-like passages and fast valve and repeated articulation work leads to the final abbreviated A section that should go as fast as one can play metronomically.  Range: c-bb'''

Bach, J.S.  Cello Suites

Though the version edited by Wendell Hoss is the version that most young people have become familiar, advanced players may wish to use the original cello part and play from that.  For those who wish a greater challenge, transposing the original part to sound at the actual concert pitch level is the height of proficiency.  Danny Katzen (BSO Hornist) wrote an excellent article about this in the Horn Call several years ago.  Check it out!

Berge, S.  Horn-Lokk (Horn Call)

Dedicated to Hornist Froydis Wekre, this selection is a must for the library of the serious hornist.  This selection is often found on competition lists.  This somewhat disjointed piece takes utmost mastery for pacing.  Though there are repeated sections, the task for the performer is to keep the audiences interest and not make this piece sound rambling.  There are some significant extended passages which must be taken in one breath.  Very fast slurred scales spanning 4 octaves will need to be woodshedded.  The recurring theme is a haunting melody that needs much experimentation so as to not sound mechanical.  The range of this piece is: D (optional) - b'''.

Buyanovsky, V.  Four Improvisations from Traveling Impressions

This set of five delightful works are worthwhile for the performer, as well as the audience.  Each of the five movements (Scandinavia, Italy, Espana, Japan, and Russian Song) create programmatic images.  It is the duty of the performer to communicate this to the audience.  There are short performance notes included by Froydis Wekre giving the soloist a heads-up on certain parameters of performance.  The most commonly performed movements are Scandinavia, Italy, and Espana.  The latter being a brilliant, fiery work that requires the utmost dexterity from the performer.  This volume is another work that should be in any performers library.
Range: E - b'''

Buyanovsky, V.  Sonata No. 2 (Finnish) for Solo Horn

This rather lengthy work (3 movements) is a tour-de-force for the hornist.  Recitatives and cadenza-like passages abound.  Likewise sections of fast arpeggiated work, articulated and slurred, will require much preparation time. Rapid open-stopped passages, as well as bended pitches are included in the technical store of this piece. Though lengthy, this work may hold
the audience's attention, being rather tonal and having some spectacular effects.  Range:  C# (LOW!) - c'''

Davies, Peter M.   Sea Eagle

One of the most significant works for solo horn.  This spectacular work is one of the more demanding solo horn works I have encountered.  In three movements, this work requires stamina and agility for the soloist.  Awkward and rapid valve work and quick, angular passages abound.  Also the hornist needs the maximum control for the wide, quick leaps that are interspersed throughout each movement.  This piece also requires significant planning in order to pace each movement.  A superior high range is essential for this work as the concluding note is a stopped high d that is supposed to taper away to nothingness.  Range:
bb - d'''.

Faust, R.   Prelude for Horn

Dedicated to Marvin Howe, this very playable work is recommended as an initial venture into unaccompanied horn literature.  The main focus of this one-movement  work is bending open pitches down via hand-stopping.  Instructions by the composer offer insight into the execution of this work.  This short work is very effective on an undergraduate recital program.
Range:  c - g''

Friedman, S.  Topanga Variations

Another work written expressly for Froydis Wekre.  The "theme" Friedman  uses is a 3-note cell consisting of a perfect fourth and major second interval.  Though seemingly innocent, this demanding work requires much agility and fast valve and articulation work.  Written in four movements, this work is interesting enough to hold the listener's attention.  The third movement pays homage to the bebop style with its swinging rhythms and disjointed passages.  This selection requires much preparation, but is worth the work.  Range:  F# - c'''.

Frackenpohl, A.  Three Movements for Solo Horn

A very playable work for the average Collegiate hornist.  This selection, written for Dr. Roy Shaberg, Former Professor of Horn at the Crane School of Music in Potsdam, NY features a collection of "characteristic pieces" titled March, Elegy, and Rondo.  March, in a typical fashion, features martial figures and is to be performed strictly throughout.  A jaunty approach will make this movement sparkle.  Elegy, as expected, is more somber.  It features wide leaps, some chromatics and much more rhythmic variation.  The Rondo is of a "hunting horn" type of piece, rollicking with compound duple and triple meter.  The tempo indicated is brisk, but to play it any slower would not convey the true spirit of the work.  Range: bb - c'''

Dzubay, D.   Solus I

A demanding work for the adventuresome hornist.  This selection features frequent meter changes, some are unusual (23/16!), but are playable. Highly chromatic and rhythmical, the hornist will need sufficient time to prepare.  At first glance, the work seems to be more difficult than it is.  While certainly not a walk in the park, it is not as strenuous as the Davies.  Dzubay writes in many effects such as accents, sforzandi, stopped passages.  I think this piece is a real sleeper.  It is worth checking out.
Range:  c - b'''

Gryc, S.  Reflections on a Southern Hymn

This four movement work is based on the Southern Harp Hymnal version of Wondrous Love.  Not only are the movements based on the tune proper, but melodic elements of the accompanying parts are also included.  Movement one, Intonation, is unmetered.  Flexibility and evoking a "mysterioso" quality is of paramount concern.  This movement is "mood music," albeit in an "otherworldly" fashion.  The second movement, Chant, is the most difficulty movement.  The difficulty rests in not only how fast the fingers can move, but how long can the hornist sustain a breath.  Thus, this has LONG phrases and blistering valve action.  The fast passages are soft, as if listening to voices murmuring in the distance.  This movement is muted throughout, but Gryc indicates that in the middle, the mute should be cracked, allowing a more open sound.  (I'm waiting for a Cabbage comment on this last sentence.....).  Pastoral is another non-metered movement, but has more motion and rhythmic variance that the first movement.  The final movement consists of a verbatim statement of the hymn tune.  Though simple, the hornist must work with delivery to create a reverent, but pensive mood.  Range:  a -bb'''

Guarnieri, M.  Etude for Solo Horn

This is short and sweet, only 2 1/2 minutes!  No overly difficult, this would be another work for an initial foray into the unaccompanied medium.  Featuring various time signatures, these changes should pose no real problem for the average hornist.  Rhythmically, the devices are relatively standard, the only "problem" being quarter note triplets.  Some stopped and echo passages are included (remember there IS a difference in tone/technique).  Range:  d - c'''.

Hill, D.    Jazz Soliloquies for Horn

In three movements (Blues-Like, Mixin, Laid Back), these movements are fun!  Featuring extended techniques, Doug has included a compendium (set of directions) as to what the various symbols mean.  I've heard Doug play these at workshops and have been very impressed with the work AND Doug's playing (CHOPS!).  Because of the rhythmic diversity and awkwardness of line, this work needs more time to prepare.  The tempos given are "interesting."  I might be able to make tempo if I consumed 5 cups of espresso per day for a week!!  Adventuresome work!  Range:  G - bb'''

Hill, D.   Jazz Set

More of the same, only now 4 movements (Lost and Found, Cute n' Sassy, Lullaby Waltz, Fussin' for Emily).  Even more adventuresome and extended than the previous work.  The movements are significantly longer and more involved.  I would imagine that only a movement or two of this set would be good to include in recital.  I think that such a long work may not sit well with the average audience member.  As an aside, for anyone interested in these works, I would encourage you to get Doug's publication, "Extended Techniques for Horn."  This is a text, with recorded examples, of newer avant-garde (as of the late 1980's) techniques for our instrument.  Range: Db - c'''

Hummel, B.     Suite for Solo Horn

I have become a real fan of Bertold Hummel's works.  Relatively unknown to American hornists, this work and his Sonatine for Horn and Piano are quality works.  In 4 movements, this work offers variety for the hornist and audience.  The movements are not too long and offer a variety of styles (Invocation, Intermezzo, Choral, Finale).  Invocation is fairly short, but incorporates much rhythmic diversity.  Though written straight ahead, the soloist will need to take LOTS of liberties in order to set up sections and organize the movement so it doesn't spin out in a rambling fashion.  Intermezzo features rapid-fire sections and some awkward leaps and chromaticism.  FLASHY! Choral is just as one would normally expect.  However, the soloist doesn't receive much respite as there are sections where the hornist needs to have an effortless upper range cantabile in several sections.  Finale pays homage to the traditional "hunting horn finale."  Boistrous triplet patterns are very chromatic and do not flow like one would normally expect.  A small flutter tongue passage is thrown in for fun.  At first glance, this movement looks harder than it is.  Though it takes time to work up this piece, the time and effort is well worth it.   Range: d - bb'''

Ketting, O.     Intrada

A wonderful introspective solo work.  This is best performed in an understated fashion, in effect, bringing the listener in to you.  A free, rubato like delivery is essential.  Great care should be taken to bring out the changes in character of the themes.  I heard a very mature and haunting rendition of this at the American Horn Competition.  Freshman hornist Jerry Welker (University of Alabama) performed a stellar version of this work. Range e' - bb'''

Kogan, L.     Kaddish

This short work is another selection that works as an initial foray into the medium of unaccompanied horn works.  Kaddish means a lament for the dead.  Written in 5/4, this only aids the hornist in a visual organization of the phrasing.  In fact, the bar lines seem to be unnecessary and confusing.  It would be too easy to play this strictly metrical.  In fact a very free, intense, and emotional performance is necessary.  Range:  d - g''

Krol, B.     Laudatio

This is another quality work that is often included on repertory lists of competitions.  This is one of the few works by Krol that seem to be readily available in the States.  He writes extremely well for the horn.  Everything I have seen by him has been wonderful.  This selection should be performed in a free-flowing manner, approximating church chant.  The interval of a half-step is a crucial thematic element in this piece.  The challenge is finding various applications of tension and release using this figure.  Take care in performing the dynamics and expression marks, as well as observing the various directions printed on the page.  This is a very effective work well within the parameters of a collegiate hornist.  Range: f - ab'''

Mishori, Y.     Prolonged Shofar Variations

This is a very interesting work that features many special effects (echo horn, stopped horn, bends, glisses).  A brilliant sounding work that is impressive to the audience.  Wide leaps and skips abound and will take diligent work to negotiate easily.  Also the ability to perform rapid articulations and the ability to play smooth, fast chromatic passages is a prerequisite.  Not overly long, this is a fine addition to any recital.  Range:  bb - b'''

Persichetti, V.     Parable for Solo Horn

This is work should be a staple in any hornist's library.  Persichetti has indicated the majority of tempo fluctuations in this work.  In fact, I find his directions are Mahleresque, that is almost giving precise instructions for each phrase or section.  It is overkill, but will be a welcome asset to a younger player.  Careful attention to all printed directions will aid in a successful performance, however observing all those instructions can initially be unnerving.  This is a very effective piece and is often found on competition lists.  Range:  ab - bb'''

Platt, W.     Monoceros (The Unicorn)

Available in manuscript only, written for Froydis Wekre.  This highly rhythmic selection is a tour-de-force for the soloist.  Many sudden mood changes make for a challenging performance.  Very brilliant, technical passages are juxtaposed to soft, static elements.  The ability to musically pace this work requires much study and trial and error performance.  The concluding section has a brisk passage that quickly alternates from stopped to open horn and is extremely challenging. If you can find this work, it
would be worth your while.  Range: eb - b'''

Thompson, B.    Of Unicorns in Curvet

Extreme agility with respect to arpeggiated passages of all types is a prerequisite before attempting this selection. Also many triplet fanfare-like passages abound in the outer sections (ABA form).  The middle section is more "cantabile," but even so major 7th leaps abound.  This angular section will need work to maintain a smooth quality to the disjunct melody.
Range:  a - b'''

Thus ends this post regarding solo horn literature.  There are omissions to be sure, but at least this will give the hornist a starting point in becoming familiar with this literature.  Happy Horning!