steps 79 to 91 in these processing operations tone generation and additional write processing operations of the performance data b are performed however since the detailed processing steps are the same as steps 54 to 66 in fig7 a detailed description thereof will be omitted as a result as shown in fig5 the recorded performance data a and the additional performance data b are mixed and written in the ram area 16a in the order of step times when key data is written in step 81 tag 34 1 34 indicating additional recording is written in the msb of the fourth byte in address increment processing in step 81 only the write address of the area 16a of the ram 16 is incremented therefore since the read address of the ram area 16b is not incremented in step 87 in the overwrite mode all the recorded performance data a in the area 16b can be preserved and are written again in the area 16a read address of the area 16b are incremented in step 87 recorded key data a is read out and written again while skipping the next key data a to be subjected to tone generation processing next therefore overwrite processing for replacing the skipped key data a with additionally played key data b can be performed fig9 shows the flow of the erase processing in step 100 it is checked if data to be erased designated by the data designation button 10f of the recording playback operation unit 10 in fig2 is new or old data if the overwritten new data is designated a flag sel is set to be 34 1 34 in step 101 otherwise i e if the old data is designated the flag sel is set to be.