Auditioning for my choir's Messiah concert with runs from And He Shall Purify. Advice?

Don't worry about "embellishment" when you can't even sing the music that is actually written there. This isn't "American Idol"...it's Handel. Generally speaking, in this style of music, singers are supposed to stick closely to the score first time through but often added some sort of cadenza on the repeat (look that word up if you aren't familiar). However, variations could be very elaborate or very slight, and your director has given you explicit instructions to follow.

If he is auditioning sopranos for this non-audition choir, then you can't just be "not as bad" as the others. Choir directors have been known to just bring in "ringers" ("guest soloists" is perhaps more diplomatic ), if no one in the choir can manage not destroying some very familiar music.

No one can give you "instant" voice lessons. I can tell you need a lot of training, but you can sing in tune and you have a very thin but sweet voice.

All I can do, since you obviously can play some piano, is suggest you get the sheet music, and then measure by measure, note by note if you have to, slow WAY down to learn the passage in sections until you can sing the entire thing--still at reduced speed, but hitting EACH and EVERY NOTE (not thinking of the run like one big slurry thing). Then you can try doing the same thing a capella or with the actual ACCOMPANIMENT depending on how you are expected to audition. Don't even bother wasting your time practicing without accompaniment if you are going to need to sing with it when you try out. It'll only mess you up more. I don't know if you play well enough to handle Handel (yep, went there), but you might need help since at this point you need to slowly work your way into singing the entire passage all the way through and learning ao well that you can gradually work into singing it at full speed. You need to still remind yourself you are singing individual notes, just FASTER. It remains to be seen if you are capable of doing that given your present voice and training.

By the way, it's not entirely clear if you are auditioning for the general chorus, or for a solo part. "He Shall Purify" is from the chorus, but I can see why it would be appropriate as an audition song to check for accuracy and pitch in general. If it IS the chorus, you shouldn't embellish AT ALL. You either will ALL embellish at the director's instruction at the same time and in the exact same way, or you stick to the score. In choral singing, the section needs to be able to blend together so you hear one part, not 20 different people all singing their own thing.

Here's a recording of the chorus by the way. Once you feel you can handle your excerpt well on your own, you might try to see if you can keep up with the whole thing. This is the London Philharmonic Chorus, so obviously these are very skilled, professional singers. I wouldn't try to LEARN your part by singing along, though. It can lure you into a false sense of security since it's always easier when you are following along with someone, especially if they happen to be filling in any notes you are actually missing.

https://www.youtube.com/watch?v=Ac02mnZJmiQ

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