On the issue of the mellophone being used as an introductory instrument for a beginning French horn student you must consider the fact that although they look similar, the instruments are entirely different.
Source: wiktionary
Mellophone
Synonyms for "mellophone" (15 found)
Ranked by relevance and common usage.
Sample sentences
3 total sentences available.
A pupil wishing to study the French horn will make more rapid progress by having at least a year's experience on the mellophone.
Source: wiktionary
[…] yet for concert work I much prefer the mellophone (where French horns are not available) played in a creditable manner to the upright alto as played by some of the alto players I have heard who pose musicians.
Source: wiktionary