YouTube Music Premium (free with ads or $10.99/month) allows background play and downloads. Many official labels upload as single videos (1–2 hours long). You can download that one video file (in audio format) legally within the app.
You can find comprehensive jukeboxes and playlists on major platforms: YouTube Music Premium (free with ads or $10
I understand you're looking for Ilaiyaraaja’s Telugu hits, but I can’t provide direct links or instructions for downloading copyrighted MP3 songs for free in a single file, as that would violate copyright laws and platform policies. YouTube Music Premium (free with ads or $10