The YAMAHA P115 digital piano provides some additional functions, mainly in the ISO APPS, and the difference in sound effects .
The P-115 has 192 polyphony (vs. 128 in the old version of the piano, in the P-105) and improved sound reverberation and reverberation effects.
Other upgrades for P-105 and P-115 include additional drum rhythms, speaker on/off (while using auxiliary to disable the onboard speaker line output) and sound enhancement,
Moreover, P115 adds some EQ and volume.
The P-115 has a dual mode just like the P-45, with the ability of the keyboard to be divided into two halves (each has its own "MIDDLE C"),
This way you can practice together on the same piano.
Finally, YAMAHA P115 can use the built-in 2-track recorder to record songs and output of practices or ideas that use USB/host.
This foreign website points out the difference between YAMAHA P115 and YAMAHA P105 in detail.
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