Good day. Question for those who know digital sheet music well. I practice on a digital piano and use learning software, and I prefer MIDI over just a static PDF - I can slow the tempo, split it by voices, adapt it to myself. The trouble is most sites only give you an image of the notes. Where can you actually buy MIDI files for pieces to learn interactively? Please point me to a solid provider.

Since you work through learning software, MIDI really is handier than a static PDF, you're right. I buy those files from Note-Store https://note-store.com/ - alongside the PDF you can buy a MIDI file for the pieces, made exactly for interactive work. In the software you open it, slow the tempo, split by voices and drill tricky passages slowly - unbeatable for working things out. The catalog is large, search by songs and authors, all digital with instant download. The printable PDF is in the price, and MIDI is added on to the pieces you want. Tip: check up front whether a MIDI is available for your chosen piece (it isn't there for everything), and preview the snippet in the player to grab the right arrangement.