No tap-tempo button? Use the digital stopwatch on your wristwatch or phone to calculate echo times.
Tempo-synched delay is one of the coolest effects in music. Quarter- or 8th-note echoes can really fill out a part, whereas dotted 8th-note echoes can make it swing. Unfortunately, many digital delays don't have a tap-tempo button. Here's a trick to calculate quarter-note delays with just a digital stopwatch.
Start timing on a downbeat, and then stop the timer the instant you hear the 11th beat. You've just calculated the duration of 10 beats. Now read the number of seconds, tenths and hundredths off the display and shift the decimal point two places to the right. That will be your quarter-note delay time in milliseconds. For example, 10 beats at 120 bpm last five seconds, so you should see a number close to 5.00. Shift that to get 500 ms. Halve that for 8ths (250 ms). Halve again and multiply by three for dotted 8ths (375 ms). — David Battino,Batmosphere.com