6. A method comprising: receiving text data; determining a sequence of linguistic units corresponding to the text data, the sequence of linguistic units comprising a first linguistic unit and a second linguistic unit; generating a representation of the first linguistic unit using a model for the first linguistic unit and a first parametric speech synthesis technique, wherein the first parametric speech synthesis technique comprises synthesizing speech using a computerized voice generator; retrieving a pre-recorded speech unit for the second linguistic unit from a unit selection database, wherein the pre-recorded speech unit comprises recorded speech configured with acoustic properties consistent with speech generated by the first parametric speech synthesis technique; concatenating the representation of the first linguistic unit and the pre-recorded speech unit for the second linguistic unit to generate audio data; and causing audio corresponding to the audio data to be output using an audio speaker.
6. A method comprising: receiving text data; determining a sequence of linguistic units corresponding to the text data, the sequence of linguistic units comprising a first linguistic unit and a second linguistic unit; generating a representation of the first linguistic unit using a model for the first linguistic unit and a first parametric speech synthesis technique, wherein the first parametric speech synthesis technique comprises synthesizing speech using a computerized voice generator; retrieving a pre-recorded speech unit for the second linguistic unit from a unit selection database, wherein the pre-recorded speech unit comprises recorded speech configured with acoustic properties consistent with speech generated by the first parametric speech synthesis technique; concatenating the representation of the first linguistic unit and the pre-recorded speech unit for the second linguistic unit to generate audio data; and causing audio corresponding to the audio data to be output using an audio speaker. 10. The method of claim 6 , wherein the unit selection database comprises a plurality of pre-recorded speech units and wherein selection of the plurality of pre-recorded speech units is based at least in part on a quality of a representation of a corresponding linguistic unit using the parametric speech synthesis technique.