Should I contribute $6000 to a IRA? I am not eligible to deduct the contribution since my income is >$74,000, but will a contribution reduce my taxable income for 2019?

[DianeC958]

No, if you contribute to an IRA and your income exceeds the limits, the contribution will not reduce your taxable income.

The contribution will be a non-deductible contribution to an IRA that when you take a distribution from the account the amount you contributed will not be taxed, but the earnings on the account will be taxed.

If you would like to have some tax benefits from the contribution you can contribute directly to a Roth IRA, if you do not exceed the income limits,($122,000 if you are Single or $193,00 if you are Married Filing Joint) or you can contribute the $6,000 to an IRA that is not deductible and then covert the contribution to a Roth IRA. 

By contributing to a Roth IRA when you take the money out at retirement, the amount is not taxable income to you.

Deductions Allowed for Contributions to a Traditional IRA

[fanfare]

"you can contribute the $6,000 to an IRA that is not deductible and then covert the contribution to a Roth IRA."

There's no tax benefit to this,

in fact it will raise your taxes if you already have an IRA.

There's no such entity as "an IRA that is not deductible".