In colloquial usage, the euphonium and tuba are generally seen as separate yet related instruments. Performers traditionally specialize in one or the other, with limited overlap between the two instruments. However, this situation is rapidly changing, due in part to two related trends: 1) the contemporary job market for academic teaching positions often requires the ability to teach the tuba, euphonium, and, increasingly, the trombone, and 2) several performer-pedagogues, such as Benjamin Pierce, David Zerkel, Chris Dickey, Matt Tropman, and Gretchen Renshaw, have demonstrated the ability to perform at a professional level on both the tuba and euphonium. This trend for equal emphasis on the tuba and euphonium also reflects the early history of the instrument. As discussed previously, the modern euphonium can be traced back to the Tenorbasshorn in Bb, built in 1838 by Carl W. Moritz off of an earlier design by Wilhelm Wieprecht. From here, the euphonium evolved alongside the tuba, most notably through its inclusion in the family of saxhorns created by Adolphe Sax. Since the tuba and euphonium were both initially developed to cover the full bass and baritone range of a large ensemble, (inspired by the range and function of predecessors like the ophicleide and serpent), the similarity of the two instruments is logical.
Taking into consideration the history of the tuba and euphonium as previously outlined, one conclusion to be made is the consideration of the euphonium as a full member of the greater tuba family of instruments. Thus, the tuba family as discussed throughout this document will consist of the BBb and CC contrabass tubas, the Eb and F bass tubas, and the Bb euphonium (or tenor tuba, as it were). The primary arguments for such a classification rest on the previously-mentioned shared provenance of the euphonium and tuba, and on the similar capabilities and playing characteristics of the two instruments.
Before continuing, a small note must be made of a few
additional instruments that may eventually be incorporated into the core tuba
family. Originally used in Italian operas during the late nineteenth and early
twentieth centuries, the cimbasso has recently made a major resurgence
in the greater tuba community. This has primarily been due to the production of
cheap yet good quality versions of the cimbasso by various Chinese
manufacturers, thus enabling a wider range of players to use an instrument that
was previously only obtainable by performers with substantial funding. The
cimbasso has not quite made enough of an impression on the greater tuba
repertoire to warrant its inclusion in this document, but this situation is
poised to change in the coming years. Another candidate for inclusion is the
traditional Bb baritone, a distinct instrument from the Bb euphonium
(despite much confusion over the two terms in its colloquial American usage).
This instrument is almost exclusively reserved for British brass bands, with
supplemental usage as an instrument for beginners. At this time, the baritone
is not enough of a separate entity to warrant inclusion, but this situation may
also change. Finally, the serpent and ophicleide have both made a
comeback since the 1970s, due to the championing of originals and recreations
of the instruments by Christopher Monk, the London Serpent Trio, Douglas Yeo,
Michel Godard, Patrick Wibart, and Roland Szentpali. The serpent and ophicleide
are similarly primed to become even more notable instruments within the context
of contemporary music, but their relatively limited usage to date has kept them
from being classified on an equal footing alongside the tuba and euphonium.
 The use of the term “tenor” here instead of the more proper “baritone” is due to two factors: 1) to reference the early emphasis and usage of the term “tenor” in describing the instrument, and 2) to avoid confusion with the colloquial use of the term “baritone” to describe an instrument of the same length as the euphonium but slightly different construction (primarily through the use of a greater amount of cylindrical, rather than conical, tubing).
 Compare the price point of these two instruments (as of 1/27/2018): the German-made Lätzsch cimbasso in F costs $17,290 (https://www.dillonmusic.com/latzsch-latzsch-cb-900-cimbasso-in-f.html), whereas the Chinese-made Wessex cimbasso in F costs $3,570 (https://wessex-tubas.com/collections/cimbasso/products/f-cimbasso-cb90?variant=42513350413).