I am currently learning Canzonetta (for tenor), and in measure 29, in brackets are the words [to next strain]. I know this probably has some sort of obvious meaning, but after watching multiple videos of others performing this solo, i have not been able to follow along past this point. I was wondering what this likely means. There is a D.S. al fine later in the song, but that seems unrelated to the text that is causing me issues with learning this piece.

After 29, you go to bar 34. It's an indication that after the "1st ending", you don't repeat the first section (note there are no dots-with-double-bar repeat symbols), but continue forward, skipping over the second ending. Later on, when you are repeating due to the D.S., you skip the 1st ending and play the 2nd ending, up to the fine.

All that is assuming we're talking about this Mozart piece: <LINK_TEXT text="https://www.sheetmusicplus.com/en/produ ... 85910.html">https://www.sheetmusicplus.com/en/product/canzonetta-21985910.html</LINK_TEXT>

There are probably hundreds of tunes called Canzonetta. In general, it's a good idea to include at least the composer's name in conversations like this.