If you already have master recording, you could sell your music without the need of anyone. You just need to find a distribution company, and there is many that you can find by googling "Digital music distribution", some distributors require a payment fee of 20$/Year to upload your songs in iTunes, Spotify, Amazon.. and hundreds of other digital stores. The only requirement is to have a quality recording and a quality Album image (3000x3000 pixels). You will keep 100% of your royalties minus the stores fees..
Hope this can help...