设计一个电子琴，支持手动弹奏、自动演奏、弹奏回放等功能，具体要求如下：

可通过8个音符键产生8个频率（还可扩展），对应8个音符（中音1，2,3，4,5,6,7和高音1），这些频率输出经放大后驱动喇叭，发出声音。当按下手动弹奏键时，按下音符键后就选通相应的频率输出，若同时打开录音开关，可将所奏音乐记录下来，然后在关掉录音开关后，按下回放键可实现演奏音乐回放；按下自动演奏键时，存储器里事先编写好的音符信息被依次取出，去选通各个频率输出，实现自动奏乐。



-Can produce eight frequency (scalable) through eight note keys, corresponding to the eight notes (Alto 1, 2,3, 4,5,6,7 and treble 1), the output frequency by amplifying the speaker driver, sound. When pressing the manual plays the key, press the note keys after gating the corresponding frequency output, if at the same time the sound recording switch is turned on, will be playing the music recorded and after the tape off switch, press the playback button can realize music playback　press automatic playing keys and memory in advance to write a good note information was successively extracted, to strobe output of each frequency, automatic playing music.