Has anyone ever used two different yeasts for one batch?

[Original Mac]

As the elderberry gods have been good this year I have plans for a two gallon batch of elderberry and blackberry port. I have 8lbs of elderberrys and 6lbs of blackberrys nicely steam juiced. To this I plan to add up to a litre of Beaverdale Cab Sab concentrate and a hint of oak. My plan is to use Vintners Harvest R56 yeast (nicked from a batch of elderberry already on the go) as it is noted for flavour extraction. Downside is it only ferments to 13% or so. Would it be complete madness be ferment down to 1010 with R56 then as I sugar feed introduce a starter of a high alcohol tolerance yeast like Lalvin EC1112? I would like to get it as close to 18% as possible so that any fortifying brandy is kept to a minimum. Can I have my cake and eat it?

Also have plans for an elderberry and chocolate port as one of my happy places involves a bottle of elderberry and a bar of Cadburys . Need to give it more thought though as to how much cocoa to add to the must to give a nice hint of chocolate as I still want the elderberry to dominate.

As always any advice most welcome

[NorthernWiner]

...Would it be complete madness be ferment down to 1010 with R56 then as I sugar feed introduce a starter of a high alcohol tolerance yeast like Lalvin EC1112? I would like to get it as close to 18% as possible so that any fortifying brandy is kept to a minimum. Can I have my cake and eat it?

Possibly.

But keep in mind that some strains of yeast are very competitive. Best case scenario, you will achieve what you want. But worst case scenario, you could end up with a stuck fermentation that will never start up again.

Lallemand publishes a very nice chart showing different yeast characteristics:

http://www.lallemandwine.us/products/yeast_chart.php

If you look at the column labeled "competitive factor", this tells you which yeasts will play nice with each other and which will try to cancel each other out. For example, using two "actives" is asking for trouble. If you have one active and one sensitive, the active will dominate the sensitive. Neutrals fall somewhere in the middle, being neither competitive nor submissive.

[SleepyDave]

ferment down to 1010 with R56 then as I sugar feed introduce a starter of a high alcohol tolerance yeast like Lalvin EC1112?

Interesting idea. But I wonder if the EC1112 would really kick of in the already subsantial alcohol environment. I reckon it would be a lot happier slowly aclimatising to the higher alcohol level from an alcohol free start.

I have tried a few brews using different yeasts on different parts of the must split into different fermenters with a view to some careful blending when fermentation is complete. I wonder whether it would work if you started one gallon with R56 and the other with EC1112 and then mixed the two when the R56 starts to faulter.

[Cellar_Rat]

I have tried a few brews using different yeasts on different parts of the must split into different fermenters with a view to some careful blending when fermentation is complete. I wonder whether it would work if you started one gallon with R56 and the other with EC1112 and then mixed the two when the R56 starts to faulter.

that's a better idea.