Sheet Music Club on Patreon
I have a monthly subscription for sheet music which I run via Patreon.
Members receive 4 brand new four-part string arrangements every month. These are new tunes which are not included on my website.
The tunes are presented as pdfs (in my standard flexible scoring of string quartet, three violins and cello, and three violins and viola). You also receive midi files, and an mp3 rendering of the midi. However, there are no recordings of real instruments, and no practice mixes included.
In the higher membership tiers, you can specify a traditional tune (or two) to be arranged each month in addition to the standard 4 tunes.
If you don't want to sign up for a monthly membership, I am also listing "back issues" in my sheet music shop for one-off purchases here.