I'm not quite sure I follow what you mean about, "punch in their unique code (which I already have stored where the album will be) and they can get the download", but you might just be trying to reinvent our wheel there.
This is what I was proposing:
1. You'd set up the pre-sale Album product without any downloads or codes, just a generic product without any special settings, maybe add an Email Message explaining that download links will be issued when the album is released;
2. Buyers of the pre-sale Album are automatically added to that product's Buyer Group list that we maintain for you;
3. When you have mp3 tracks ready to sell:
A. If you're selling tracks individually, set up each track as a separate product and upload their respective mp3 files, then edit the pre-sale Album product's settings to enable "Package files from other products" and select the tracks that should be issued as a "bundle" of downloads for that product; ...OR...
B. If you are not selling individual tracks, then you could just combine the album tracks into a single .zip file and upload that to your Album product as a Single File Download.
4. Use our Updates/Newsletters service to send the Buyer Group list for the pre-sale Album product an email message, each containing a unique link to reach the thank-you/download page for the newly "bundled" album;
5. Pre-sold buyer clicks the unique link in their own Update email, reaches the thank-you page, downloads the album .zip or individual tracks (whichever you'd set up) -- each buyer's unique links will automatically expire after the number of download Attempts or Hours (whichever comes first) that you defined in the Album product's settings.