Improve quality of generated songs and download individual stems

I would like to improve the quality of already generated songs and have the ability to reprocess and download them. The instrumental stems currently sound poor. It would be beneficial to have the ability to isolate and download the stems for each instrumental part, such as Bass, Solo Guitar, Lead Guitar, Rhythm Guitar(s), Acoustic Guitar(s), Strings, Keys, Piano, Organ, Percussion, and each Drum part. Additionally, having the ability to extract and download MIDI files for each instrumental stem, set or change key signatures, and download chord progressions would be very useful.