This will be one of the few times where I feel that I will need to have a debate on the merits of two instruments. Usually, if two instruments of similar pitch exist, I would say to use them both for their merits, but not here.
Traditionally, the Alto Clarinet has been an instrument only for the band, while the Basset Horn has been an instrument only for orchestral and chamber music. Here we get to the real difference between the two. Professional clarinetists look at the instruments differently. The Basset Horn is viewed favorably, while the Alto Clarinet is not. Manufactures know this as well. The Basset Horns being produced today are far superior to the Alto Clarinets being made. Known design flaws in Alto Clarinets have gone unnoticed, or been neglected for at least thirty years.
The ranges of the two instruments differ slightly as well. The Alto Clarinet descends to a curious low concert G-flat, while the Basset Horn descends to a concert F, which is a minor second lower even though the instrument is pitched a major second higher.
In general, the difference between the two instruments is said to be in the bore size. The Basset Horn is supposed to have a narrow bore while the E-flat Alto Clarinet has a wide bore, but this isn’t always the case. Some Basset Horns will have larger bores than some Alto Clarinets. It all depends on the manufacturer. For example: a Yamaha Alto Clarinet will have a bore of .670 inches while a Buffet Basset Horn has a bore of .673 inches.
I think it is time that we abandon the E-flat Alto Clarinet in favor of the F Alto Clarinet, for that’s what the Basset Horn really is nowadays. The miniscule differences in bore design are usually only noticeable to the player.
Let’s now think of the possibilities of the F Alto Clarinet. When symphony orchestras purchase this instrument, they almost always buy a matched pair. Most of Mozart’s music and some of Strauss’ utilize two parts. As bandesterators, we should take advantage of this. Why not have two F Alto Clarinet parts in our work? The sound of the instrument is beautiful (after all, it was Mozart’s favorite!).
The complaint from band directors about the uselessness of the Alto (either size) comes from their own hand and usually not the composer’s (though many composers can share some of the blame). When you use two dozen B-flat Clarinets and only one Alto Clarinet, the whole of that unique sound will be lost! 24:1 are not great odds to be heard. How about instead 6:2 (4:2, 2:2)?
I cannot think of any member of the woodwind family with which the Alto Clarinet will not mix. Grainger showed us that the most disparate instrument, the Piccolo, makes for a haunting combination. Mozart used it to great effect with the Bassoon in his Requiem (where the entire woodwind section is 2 F Alto Clarinets and 2 Bassoons). With English Horn (or any low oboe), great moments of poignancy are derived. Many composers have also used it with the Horn, where it fills in as a lower voice. The same can be done with the trombones (when played at piano).
Do not just confine your writing to have the Alto Clarinet be just a member of the clarinet ensemble. Use it as a solo voice and with other instruments.
Mozart Divertimento for 3 Basset Horns – Note: one of the instruments is actually an E-flat Alto. Tell me if you can hear the difference? I can’t.
Introitus and Kyrie from Mozart’s Requiem
Richard Strauss’ Sonatine in F – contains an inportant part for Basset Horn. Score is available on IMSLP, but is not public domain in the U.S.
Finally, the most invaluable piece of literature on the net about the Alto Clarinet and Basset Horn can be found here.