Hide and Seek has a really unique sound. Heap recorded it late at night in the studio after her laptop had died and she couldn't use traditional software. She turned to a digital vocoder, having little experience using one before, and was able to compose this piece in one try. The vocoder layers Heap's voice and turns it into the 'instruments' giving a song a distinct a cappela feel. The sound of the song is very technical, it feels almost autotuned but the melody is so incredible and the tone created by the vocoder fits the meaning of the piece. The song is about Heap's experience with her parents divorce, a sort of fracturing feeling unlike anything else and Hide and Seek really embodies that feeling.
Lifeline, another Imogen Heap masterpiece, is really an amazing piece. Every 'instrument' in the song was created from found sounds or recordings of natural sounds. The song was also crowdsourced, meaning Heap sent out the message to her fans that she needed recording of random sounds from their daily lives and they submitted the recording to her to be chopped, edited, and used in the song. Some of the example sounds Heap used were the train pulling into the station, ETC, ETC. The coolest part about this song in my opinion, is that Heap used the sound of her niece's heartbeat as a prominent instrument. Her brother submitted a recording of the baby's heartbeat in the womb. Listen closely to the very beginning of the song - sound you hear as a sort of percussion behind the melody is the heartbeat.