First off, just so no one is left behind - a digital distributor is a company that takes your uploaded music to their platform and helps you get it into all of the prominent global downloading platforms (iTunes, etc.) and streaming platforms (Spotify, YouTube, Apple Music, etc.).
There are many great digital distributors out there, but the most common recommendation we have is for artists in regards to choosing a digital distributor is to work with Distrokid at the Artist Plus Plan. It's around $38 per year and gives you unlimited uploads, the ability to set a pre-order date for your song, and loads of features that offer way more value than the annual subscription price.
TuneCore and The Orchard are our other two favorite digital distributors at the moment.
We do not recommend artists work with CD Baby. While they have exceptional customer service compared to other digital distributors, their upload speed is very slow (as of this message, their current upload speed is 7 weeks, meaning you'd have to set your release 7 weeks in advance to have your song upload in time). We’ve had many artists with songs that didn’t get distributed by CD Baby in time for their release date because of the slow speed and not uploading with enough time as CD Baby requests.
We only recommend artists transferring their discography from their current digital distributor to another digital distributor (like Distrokid) only when they are not actively releasing music. If you are currently in a release cycle, we highly advise you to wait until a multiple week dead spot before transitioning (for a lot of artists, this would be around December/Christmas time).
Here's more infromation how to change to Distrokid: https://support.distrokid.com/hc/en-us/articles/360013648133-I-m-Switching-from-a-Different-Distribution-Company-to-DistroKid-What-s-the-Process-
Here's a link to get 7% off your signup with Distrokid! https://distrokid.com/vip/seven/1061288