Final answer:
A combo is a group of three to four solo jazz musicians who play improvised jazz music, unlike embouchure or transposing which are related to playing techniques and music theory respectively.
Step-by-step explanation:
The group of three to four solo jazz musicians who play improvised jazz music is known as a combo. A combo typically features a selection of instruments such as the saxophone, piano, bass, and drums, and they perform in a more intimate setting compared to larger jazz ensembles. The embouchure refers to the way in which a musician applies the mouth to the mouthpiece of a brass or wind instrument, and transposing is the act of changing the key of a piece of music. Both of these terms are also related to music but do not describe a group of musicians.