There are concerts available, both local and across the world! Many are virtual. Here are some examples you may want to check periodically or save in your bookmarks.  Let us know of others you believe we should add!
The Colorado Chamber Players

Colorado Chamber Players, a fully-professional mixed chamber ensemble, delivers intimate, captivating performances of classical music in locations across the Denver area. One of Denver’s finest chamber music ensembles, Colorado Chamber Players includes many top level musicians in the Rocky Mountain region. The group’s core is string quartet, double bass, flute, oboe, clarinet, piano, harp and guitar.

https://www.coloradochamberplayers.org
Parish House Baroque

 

With a core formation of baroque violin, recorders, baroque cello, and harpsichord/organ, Parish House Baroque continues to strengthen our reputation for highly expressive performances and compelling programming.

https://www.parishhousebaroque.org/

Seicento Baroque Ensemble

 

This ensemble is based in Boulder, Colorado and is well known here for their beautiful and inspiring performances.

https://www.seicentobaroque.org/listen/

Lone Tree Arts Center

The arts center presents a variety of shows throughout the year.

https://www.lonetreeartscenter.org. https://www.lonetreeartscenter.org/shows
Happy Hour Concerts

 

These concerts are given at happy hour by small chamber groups, at Epiphany Lutheran Church (pandemic permitting).  Please check their web site for seat availability and online instructions.

https://happyhourconcerts.org/

Baroque Chamber Orchestra

 

One of the best-known chamber orchestras in the region.  I will let these sample recordings speak for themselves.  If you can't see them live, they do have recordings available.

Baroque Chamber Orchestra

GroupMuse
 

Let's not forget this one!  They quickly adapted to a virtual forum, providing performances from all over the world! They are now beginning to return to live performances, so the best of both worlds appears to be available.
https://www.groupmuse.com

The Boulder Arts Festival
This is a local organization in its 40th season, "Boulder Bach Festival: Colorado's finest in early music".

boulderbachfestival.org