I also do both. I prefer not to have cantors, I feel it is a waste of the budget and it is hard to find someone who can chant properly. I'd rather just do it myself and use the budget for helping out the volunteer choir with some more experienced voices.

I have been in situations where I did this a lot and in other situations where I did this very rarely, depending on the parish. For 4+ years recently, it was very rare, because they tried to have semi-pro, paid cantors for every Mass, so I only did it in a pinch. At other points in my career, I did it every Sunday.

I wish my MD would act as cantor for funerals. The one older woman who serves as cantor for funerals sounds as if she could wake the dead with her shrill voice.

Anywho…

What I found helped me immensely was every time I'd sit down to practice the organ, I'd spend some time flipping through the hymn book sight-singing and playing random hymns. I did this until I was comfortable picking up any hymn and playing and singing it without prior practice (not an excuse not to practice).

I have encouraged all my students to do this. They don't, and then they text me horror stories of how they struggled to play a hymn they didn't know, and then I gently remind them that I specifically asked them to implement this routine multiple times and this is why...

I have evidence!

Nowadays I don’t mic up, tho. Actually enjoy doing this sometimes.

Reminds me of when I employed three musical talents. Guitarist, organist and vocalist… except it was all from one person …simultaneously.

TCJ that's good advice.

I've played piano my whole life and acquired a home organ two years ago so I could fill a void of many parishes in our rural area lacking an organist. I can manage some common hymns pretty well if I need to sing, but when I throw in something like Now Thank We All Our God my muscle memory doesnt follow the music naturally. I think if my organ skills were improved it would help, but with young kids finding practice time is tough. I've made a lot of progress but still significant room to grow to match my ability on a piano.

I was hoping someone would say "a church document says you should only have one role during Mass." I'll keep plugging away

For me, it's varied from place to place. My first job, I did it all the time for daily Mass but rarely on Sundays (it's also the only place I've been that has expected an organist for daily Mass). When I moved to Florida, the first place I was at expected it for all weddings and funerals, but not on Sundays. At the place I left about a year ago for my current position, I regularly had to do it, usually at the early morning Mass but sometimes others, rarely for weddings and funerals. Where I'm at now, I've had to do it only once on Sunday when the scheduled cantor got her schedule mixed up and came for the next Mass instead, and occasionally in Spanish.

No matter the situation, it's a good skill to pick up as an organist, even if you wouldn't be caught dead doing so in public. It helps me when practicing hymns in terms of breathing/lifting and tempo. When you have to sing from the bench, your singing technique can be somewhat compromised and you become closer to the untrained person in the pew, which isn't a bad thing when you have to lead said people.

Legend says that Frescobaldi was famous for cantoring from the organ bench while playing.
So there is quality precedent.

So far I have not been both the cantor and organist.

What I have done is sing along with the choir as part of the ensemble, so I am singing and playing the Gloria for example. I also teach them the melodies of new pieces by playing and singing, particularly the Entrance Antiphon, Responsorial Psalm, Alleluia and Communion Antiphon.

Well, today our cantor called in sick at the last minute...and I had to step in and sing his parts.

It took a lot of concentration, and I would have liked to have more time to prepare than an hour before Mass, but it worked out OK.

To those of you that are both organist and cantor all the time, my hat's off to you.

When I have a cantor, I tend to sing with them as a "choir" of 2. I find it supports the congregational singing better the more sound I have in the loft and counteracts the "cantor diva" effect. If something is new or particularly difficult, I will drop out if I need to focus more heavily on the organ part, and I have the cantor sing solo on incipits/psalm verses generally speaking.
Being able to do that has allowed people who weren't quite comfortable singing as a cantor to step up, and now several of them have become really solid!

I didn't do both. I had the good sense to realize my voice declined in my fifties and I quit singing solo. Too many "divas" seem to not know when to give it up.

This arrangement of Cantor and Organist in one is so prevalent in my region, that people often assume i also play the organ when i only do the singing.