That just depends on where you want to add th new data. You can use punch in recording and add date anywhere you like within the track, Do you mean make longer by adding to the end of a recorded track or at the begining of a recorded track.. If so this is again accomplished by punch in recording. If you attempt to overdub any data over existing data (in hopes to get them to play together), the new data will replace the old.. However the PSR's do allow track merging, which in a way is like overdub recording. You record two tracks, merge them together, and you free up another track for recording...
Squeak
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GEAR: Yamaha MOXF-6, Casio MZX-500, Roland Juno-Di, M-Audio Venom, Roland RS-70, Yamaha PSR S700, M-Audio Axiom Pro-61 (Midi Controller). SOFTWARE: Mixcraft-7, PowerTracks Pro Audio 2013, Beat Thang Virtual, Dimension Le.