The ZX Spectrum beeper is a simple audio coil controlled by the Z80 processor.  It is present in all models but more popular with the 48k edition before the introduction of the AY-3-8912 soundchip (more or less identical to Atari ST's YM2149).

Recommended editors:
- '[l[http://freestuff.grok.co.uk/beepola[Beepola] (Multi-engine; Windows, known to run in Wine) 
- '[l[http://www.worldofspectrum.org/infoseekid.cgi?id=0008523[Orfeus Music Assembler] (native)
- '[l[ftp://ftp.untergrund.net/users/shiru/zx/phaser1.zip[Phaser1] (native)

also available:
- '[l[http://alonecoder.nedopc.com/zx/index.html[Beep Tracker] (native) 
- '[l[http://www.worldofspectrum.org/infoseekid.cgi?id=0017604[Creador Musical II] (native) 
- '[l[ftp://ftp.untergrund.net/users/shiru/zx/musboxte.zip[Music Box T.E.] (native)  
- '[l[ftp://ftp.untergrund.net/users/shiru/zx/msynthte.zip[Music Synth TE] (native)  
- '[l[ftp://ftp.untergrund.net/users/shiru/zx/stocker.zip[Stocker] (Windows) 
- '[l[http://www.worldofspectrum.org/infoseekid.cgi?id=0008487[YU the Music Box] (aka The Music Studio)
- '[l[http://www.worldofspectrum.org/infoseekid.cgi?id=0012538[ZX-7] (native)