Most iOS devices come with a headset, which includes a microphone. However, if neither your headset, nor iOS device contains a microphone, it will be necessary to purchase a headset that contains one. Singer's Mate can be used with headsets that do not include a microphone as long as one is built into the iOS device.
The main reason the headset is necessary is that the built-in microphone and speaker are in close enough proximity that the microphone will pickup the accompaniment playing over the speaker, instead of your voice. Plugging a headset into your iOS device allows you to hear the accompaniment, while Singer's Mate is detecting the pitch you are singing.
The second reason is more difficult. In designing Singer's Mate, we chose a pure sine wave as the accompaniment, since it is easier to discern the pitch of a sound with no harmonics. The speaker's frequency response differs between iOS devices and in the lower ranges around C3, that is, one octave below middle-C, the volume for speaker output maybe too low to listen to. As a result, depending on which iOS device you are using, you may not be able to review or listen to a piece by playing it through the built-in speaker. This can be remedied by connecting your device to external speakers. However the frequency response for all of Apple's headset's is very good over the full singing range, so officially we only support use of Singer's Mate with a headset.
Previously the lowest pitch that Singer’s Mate could accurately detect was G2, somewhere around the bottom of the baritone range. However, with recent improvements, Singer’s Mate can now accurately detect and measure pitches down to D1 (36.7 Hz). This is one note lower than the lowest note on a double bass and much lower than the lowest note in the standard opera repertoire, D2.