Is downloading music from tubidy legal?

Maybe... It depends on where you are downloading the music from.

Some music is free to download and it is legal, but, not all music you can download for free is legal.

If you download the music from a website that you pay for each song then it is legal.

If you are downloading music for free from a file sharing website then that is illegal.

If you download the music from a website that has legal rights to distribute that music and they give it free of charge then it would be legal.