I prefer "Christian volunteers" over more "professional" musicians. But I am speaking of simpler tunes with basic instruments (guitar, drums, maybe a keyboard). Last Sunday the church only had an acoustic guitar and a violin.
I believe the congregation itself should supply musicians from within the congregation. It should supply the pastor as well ("choose from among you").
I believe there is much to be said here which strikes at the heart of the matter. We are obsessed with complexity, with theatrics and polished performances to the point where we need to hire "professsional musicians" in order to pull it off! It matters not whether they believe or are living a life of holiness, they really know how to "shred" that guitar and that will pack the seats on Sunday! This is where I have become rather contemptuous of so-called "Modern Worship!"
What you are saying about "Simplicity" pretty much nails it. I am not there to show off to the congregation how great of a guitar player I am. I am a worship participant leading others to worship along with me. Complexities of arrangement often get in the way of the message of the song or hymn plus it often forces people to play above their ability which can bring disastrous results!
I recall back in the 80s and 90s when there were some really great anthems and choruses being sung (Rich Mullins "Awesome God," Jack Hayford's "Majesty," and all of those wonderful Maranatha! Music scripture songs and choruses) and the best thing was we were all singing out at the top of our lungs plus we remembered and sung them throughout the week! Something happened and I believe that modern worship music was well on its downward trajectory by the time I picked up my Stratocaster and went "Contemporary" back in 2003!
I am all for the congregation supplying its own musicians and if there are none in the congregation, perhaps the Lord is calling them to sing acapella for a while! Pastors ought to emerge from church congregations and not just "magically appear" from seminaries but I am content if we could just ensure the pastor is first and foremost a functional member of the church and not someone on the outer fringe who has been hired by a "Pulpit Committee."