or wind a coil around the tuning fork, hook it to the freq counter, strike the fork and hold it to a magnet. if there is enough wire, you can get enough voltage to feed the counter's chips.
the reverse was used in the 30s for master clock timing in radio. General Radio had an oven-mounted tuning fork driven with big-boned triodes that output 115 volts at exactly 60 cycles to power clocks. the triodes ran magnets that vibrated the fork.
Also the basic theory of operation for an Accutron watch. Later adapted by Seiko for the Pulsar quartz watch that is used by nearly everyone today.