The Orchestra Header contains global information that applies to all instruments and defines aspects of Csound output. It is sometimes referred to as instr 0, because it behaves as an instrument, but without k- or a-rate processing (i.e. only opcodes and instructions that work at i-rate are allowed). An orchestra header statement operates once only, at orchestra setup time. It is most commonly an assignment of some value to a global reserved symbol , e.g. sr = 20000. All orchestra header statements belong to a pseudo instrument 0, an init pass of which is run prior to all other instruments at score time 0. Any ordinary statement can serve as an orchestra header statement, eg. gifreq = cpspch(8.09) provided it is an init-time only operation. Statements that are normally placed in an orchestra header are: 0dbfs A4 ctrlinit ftgen kr ksmps massign nchnls pgmassign pset seed sr strset For example, a Csound header may look like: xxsr = 44100 kr = 4410 ksmps = 10 nchnls = 2 0dbfs = 1 massign 1, 10