Tuba player, e.g

• Band member
• One who plays without vocals
• Helpful to first violinist for example
• Someone who plays a musical instrument (as a profession)
• Fan must start in line to see player

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
1823, from instrumental in the musical sense + -ist .

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Instrumentalist \In`stru*men"tal*ist\, n. One who plays upon an instrument of music, as distinguished from a vocalist .

Longman Dictionary of Contemporary English Word definitions in Longman Dictionary of Contemporary English
noun EXAMPLES FROM CORPUS ▪ All the instrumentalists, of course, weave solos through this fabric of sustained notes, but the focal point is Threadgill. ▪ First, the ballet livrets of this period treat the instrumentalists as members of discrete groups. ...

Wiktionary Word definitions in Wiktionary
n. One who plays a musical instrument, as distinguished from a vocalist