The idea of a solo for one instrument out of a group seems to have been quite foreign to medieval music. In fact, composers usually did not assign parts to specific instruments.
violin
sonata
sonata
lyres
The tune Greensleeves can be played by a myriad of instruments. It can be played by a group or on a solo instrument. It can even be sung.
Johann Sebastian Bach wrote immense amounts of music, for organ, for solo clavier (a forerunner of the piano), for solo violin, solo cello, solo flute, for different ensembles of instruments, for solo voice, and for chorus with instrumental accompaniments. In short, he wrote for every instrument in existence at his time.
It is an ensemble piece with solo instruments featured, the piece cannot achieve its purpose being played as a solo.
Entertainers in the medieval period might sing, dance, play musical instruments or tell jokes.
two solo trumpets
Bach Trumpet
concerto
A concerto is a three-movement form of composition with a solo instrument playing alongside an orchestra. A concerto with many instruments playing in a " solo group " is called a concerto grosso.