Database scheme, autoincrement

I would go with a computed column for PhraseVersion, that will take the count of rows with the same PhraseID and Id lower or equal to the current row.

To do that, you need to create a UDF to calculate the PhraseVersion:

CREATE FUNCTION dbo.GetPhraseVersion (
    @PhraseId int,
    @id int
)
RETURNS INT
AS
BEGIN
    RETURN (
        SELECT COUNT(*) 
        FROM T 
        WHERE PhraseId = @PhraseId 
        AND Id <= @id
    )
END
GO

Then, Create the table with the computed column:

CREATE TABLE T
(
    id int identity(1,1),
    PhraseId int,
    PhraseVersion as dbo.GetPhraseVersion(PhraseId, id)
)

GO

Now for the test – insert 4 records:

INSERT INTO T (PhraseId) VALUES(1),(1),(1),(2)

Select:

SELECT *
FROM T

Results:

id  PhraseId    PhraseVersion
1   1           1
2   1           2
3   1           3
4   2           1

You can see a live demo on rextester.