I remember always being surrounded by music when I was a child growing up in Los Angeles.  Whether it was my mother playing her many classical music LP records (for those too young to know, these were 12" vinyl discs which reproduced sound through the amplification of small vibrations from a needle tracking the disc's spiral groove!), or then it was her own teaching of rhythm to a bunch of us noisy kids by handing us various percussion instruments (maracas, bongos, toy xylophone, even a 4-quart saucepan and a wooden spoon would do!) and having us accompany her while she played familiar songs on the piano with my father singing along.  When camping, we would always have sing-alongs by the fire as she played the guitar.  I suppose all these things contributed to my love of music--even my father's singing!

Now, if you don't count my all-to-brief attempt at structured piano lessons as a child, I guess you could say that my background in music performance officially started in junior high school with the trombone.

You can play duets with only one horn!

I learned to play the trombone as part of a beginning band class.  I originally wanted to learn the trumpet.  Of course, so did many of the kids.  The wise music teacher gathered all the kids who wanted to play trumpet and, one at a time, handed them one and said, "Alright, blow!"  Some naturally hit higher notes; they were given trumpets.  Others, including me, blew lower notes and, as a result, were given a choice between a trombone, a baritone horn, or the tuba.  Well, the baritone looked to me like a small tuba (popular style of they day shown at right) and the tuba was, well, a lot more metal than I wanted to carry around.

Further innovation in the mid-15th century resulted in the now-familiar curved parallel-tube slide which, because it was doubled back, was capable of filling in notes that were not playable on the straight slide trumpet. 

In the 15th century, we also find the first music texts with precise instrumental descriptions (other than for the organ).  Among them, a brilliant and stirring 'tuba gallicalis', a fanfare on a broken chord of C Major for three sackbuts.

The earliest known illustration of a trombone appears in the late 15th century painting "The Assumption of Virgin" by Filippino Lippi in the church of S. Maria sopra Minerva, Rome.  A monochrome partial detail appears at left. 

Shown at right is a plate from Michael Praetorius's Syntagma Musicum (Treatise of Music) of 1618, showing: numbered 1&2. bass trombones in F (note the handle to facilitate the long slide reach); 3. tenor trombone in Bb; and 4. alto trombone in Eb. 

Instruments number 5-7 are curved cornetts; numbers 8&9 are straight cornetts; numbers 10-12 are trumpets and 13 are crooks used to change key.

The descant trombones were eventually replaced by cornetts and later trumpets.  In the end, it has been the tenor trombone which has become most prevalent.